Use one of these!    

Use one of these!

"what's the easiest method you've come up with"

  I like to paint my wheels in the car while spinning them so I just turn the car upside down, spin each axle and spray, then when all  the wheels look right I clean the treads with a Q-tip and water. If the paint has set too much for water I usually just wait and clean the treads with a dremel and wire brush or sometimes I just leave the light overspray on the wheels and don't worry about it. ( This method works well for O, S, and HO scales where the wheels are big enough to spin easily, for N scale I've been just painting the wheels carefully with a small paint brush and scraping any stray paint off after they dry).....DaveBranum

Kevin K. uses the Floquil

Kevin K. uses the Floquil markers to paint his wheels and then uses weathering powders - they look great!  He shows how in his excellent weathering PDF which is free.

Cool tool

I like it. Where'd you get that tool Nelson?

-Hunter

Paint markers

I think paint markers take the award for easiest method.  Like Kevin K, I only use paint as a base for powders that I apply later.  

-Hunter

Instant Weathering

I use Instant Weathering powder to weather my wheels often.  I use the darkest brown, and dab a microbrush in a little water before picking up some of the powder with it.  It can then be painted on the hub of the wheel, either loose or while rotating it in the sideframe.  It looks good when it's dry.

Easy way to clean wheels

I usually paint my trucks by sticking the pointy end of a pencil into the mounting hole and then rolling them back and forth on an old piece of track mounted on a lazy susan while spraying them the appropriate colour. I then transfer the truck over to another piece of track with a paper towel soaked in lacquer thinner laying across it and roll the truck back and forth over the towel. once the towel gets to dirty just slide it over a notch and add some more thinner. Cleans the wheels in about ten seconds. You can paint a whole whack of them in short order.

"Cool tool"?

 The problem I can see with that is how does one paint the back of the wheels without getting axle shadow from spraying with them static? ....DaveBranum

Tool

The Plexiglas wheel holder comes from AMB, the people who do the great wood laser-cut kits. They are on the HO scale index page. A couple other companies make a similar tool.

http://www.laserkit.com/laserkit.htm

It lets you put a nice layer of paint on both sides. A paper towel is enough to clean up the axle tips.  I like to do a couple dozen pairs at a time and save them for kits as they get built.  Microbrushes also make a nice job of painting wheels, as well as weathering them.

Walthers stocks them in several models for HO

http://www.walthers.com/exec/search?quick=wheel+mask&x=11&y=10

They're great for putting quick layers of weathering on your wheels.  As for the axle shadow, spraying from several different angles cures that.   Remember that NOTHING in nature is uniform!

Wheel Painting Holder

  The AMB jig is really great.  There are two sizes(33" & 36" wheels), and two models - One for I-M/ReBoxx wheels, and one for Kadee/P2K wheels - I cracked one of my 33" I-M ones putting P2K wheels in it!  I guess they have a little different taper to the profile.

  Modeler Choice also makes jigs for making your wheels  Theirs holds 8 wheel sets, but it is a little clumsy to get all those wheel sets in!

Jim

Wheel Jig

Buy a jig and a package of wheels. Personally I use the semi-scale from Intermountain. Narrower profile but not so much that it presents a problem when running across multiple modules built by different people with different commercial track. load up the jig and hit the wheels with something like ruddy brown primer or boxcar red, then follow up with weathering powders. Lather, rinse and repeat until you've done the whole package of wheels. Place in bin and replace wheel sets as you weather cars. Or that's what I do. 

Matt

Another source

Minuteman Scale Models sells a jig similar to the AMB for a little less money.  http://www.minutemanscalemodels.com/category_s/54.htm