I use...

one of two methods:

1. 90% isopropyl alcohol on a q-tip and scrub off the lettering
2. very very fine sand paper and a light touch to scrub off the lettering

Either way, it's tedious.

Or there's always the trusty paint patch

Oh no, much better

Get an eraser off a pencil, or better one of the stick erasers and "erase" the number.  Use an eraser shield (old drafting part) if you need to.  For an example of how it works, see my article on the City of Miami in the July 2013 Model Railroad Hobbyist magazine - there are photos of doing exactly what you are asking.

I've used oven cleaner to

I've used oven cleaner to remove lettering. I often use this on Athearn blue box cars.

Getting the lettering off is

Getting the lettering off is easy.

But if you need to re-number then that's a problem.  I buy identical cars sometimes with the intent to renumber.

My approach is to scan the road number and then permutate the digits using the digits I have and create decals.  The problem with this approach is that you only have a very limited number of digits you can use.

How does a person go about matching font sets?????  I'm no printing expert I can't tell?

Any suggestions.

Again, go to my article in the July 2013

Model Railroad Hobbyist, where I deal with that very same issue with my City of Miami train - though in that case I was doing car names, as well as numbers.  But the easy way is to use a flatbed scanner to capture what you have, then photoshop (or what you have) to change out the numbers.  When printing the decals, I have found that printing about 3x the number you need works out.

Since you are scanner the original font, there you are.

If you have an existing car

If you have an existing car say with oad number  1923,  you don't have a sample of a 0,4,5,6,7,8 digits.

So how do you create a car number like 1927, or 1946,.....

That was my point above.

you wade thru hundreds of fonts

you wade thru hundreds of free fonts until you find the one that matches.

or you take the plunge and buy from a specialty font site like http://www.railfonts.com

Either way, your results will be much much better than scanning from the model

MicroSol

There's a much easier way which works (based on my experience) on (recent) Athearn and Atlas models: MicroSol.

Cut a small piece of tissue paper to just cover the numbers or lettering to be removed and soak the tissue in MicroSol. I mean really soak. And keep it soaked, topping up every 5 minutes or so. After about 20mins to a half an hour, you should be able to remove the letters with a stiff brush or my preferred tool: a toothpick.

Cheers,

Colin

yup

 But you can create 1922, 1921, 1929, 1992, 1993, 1991, 1999, and many more.  Oh, and maybe you can rotate the 6 to become a 9, depending on the font.  A 9 or a 3 can also be made into an 8 many times.

"But if you need to re-number

With the demise of the commercial decal supply a company that prints decals on demand would be very handy. Something like the shapeways plan where one could upload photos of the decals desired and they would turn them into a printed product and mail them to you. I have a lot of cars that could use new numbers or whole new paint schemes if the decals were available.......DaveB 

well there's an idea

oh wait, countless custom decal makers, including myself, do that every day Dave.

How about this.........

I remember when I was a kid, models came with apply yourself decals(planes,cars,tanks and naval ships did).  You had number sets not just a preapplied decals.  What the F happened to those good old days.  The only  one that even comes close to this is Accurail with a fee of $4 you get exactly that, a set of numerical digit fonts.

A suggestion to rail model manufactures, how about decorated with self applied road number decal SETS.  When I say SETS I mean SETS.  ie 4 of each digit for each application.  Something the size of a playing card which probably costs the same.

How about undecorated but with self applied decals(lettering, data, number SETS).  No more boxes of six but a person can buy 2 or 3 or 4 singles and still have different road numbers or road names.  You actually might get more sales this way.

Sorry but this is a bit of a pet peeve of mine, and a problem in the hobby.  So coffee talk and discuss!

Yes

and I bought a bunch of Accurail stuff for that reason, but then I also just finished aquireing 40 34 foot coal cars from Athearn - all 40 with unique numbers applied at the factory!

"oh wait, countless custom

  Maybe they need to advertise better then because all the one's I see only make decals in certain roads they like, or they go out of business after a few months, or they need certain kind of files to print, or they want a fee that costs more than the car to get a decal ready to print, etc.    A place run online like Shapeways would have top of the line printers and software that could scan a photo of a car and clean it up and  turn it into decal ready files automatically so the average modeler could afford some sets, it would also have files that other users have provided so we can buy copies of their purchases. I don't know what it would take to start something like that but if technology gets there soon I'd be ready to buy......DaveB

problems with copyright

Dave, The problem with such a service would be all the copyright issues you'd run into marketing other peoples artwork. At shapeways, they are dealing in "shapes", not logos and trademarks.

I won't discuss costs or details here since I am not yet an advertiser (soon!) but feel free to contact me off list if you like.

Solvaset and Scotch tape

I recently removed stamped road numbers fron BB by wetting the stamping with Solvaset, letiing it set for a couplr minutes, blotting with a tissues, follwed by an overlay of Scotch tape. Burnish the tape over what you want to remove, give the tape a vigorous tug and there you have it. 

Remove lettering

I use full strength Pin-Sol to remove lettering.Just dab some on the lettering to be removed,wait a little while for it to loosen up the lettering and rub it off.As a bonus,it will leave a smooth surface if you are going to apply new decals.You can also soak cars in full strength Pin-Sol to strip paint with no damage to the plastic.

Something I have done

Check out this method I use.  It's not for everybody but I like the results.

https://forum.mrhmag.com/post/restenciling-cars-simple-but-effective-way-12192745