Novices be warned, building a model railroad is a messy business. Owning a good vacuum cleaner during layout construction will benefit you throughout the layout's life. Spend a decent amount of money on a good one. Why? Here are a few good reasons...
Using the family vacuum will cause you grief with the spouse. It won't be there in the closet when she goes looking for it. It will have plaster dust all over it. It will be full every time she needs it. Bad juju. So get your own.
Get a canister vac with a long flexible hose. You don't want to be dragging heavy hoses over your delicate scenery later on. If it has a 2 inch diameter hose, buy a transition coupling and a length of smaller hose to use with it. You will appreciate the extra length. (No improper jokes please.)
For a larger layout, get a large shop vac on rollers. Smaller layouts can use the smaller versions of these, without rollers. I have one I nick-named R1D1. If you get a small one, WEIGHT IT DOWN. Mount it on a thick board or heavy base so that pulling on the hose won't turn it over. These things are worse than a new dog on a leash. I know a guy that poured 2 inches of plaster in the bottom of his tank to keep it upright.
Make sure the one you buy comes with disposable bags, and a separate filter, preferably a HEPA filter. There is nothing worse than having your vac spewing dust all over the layout. USE THE BAGS and FILTERS. All of the shop vac style vacuums can be ran without bags and filters primarily for water pickup. You don't want to use it that way. It becomes volcano of dust.
OK, so now you have spent the money, how do you use it? First, the obvious. You sweep the floor, vac the roadbed prior to tracklaying, etc. That is the obvious stuff and I won't go into specifics, but understand all of these things gain extra points with the spouse because you are cleaning up your messes as you go.
One thing I do is use some home-made hose reducers and a length of 1/2" tubing to clean up stray ballast prior to gluing it down. If the suction is too great, lift the lid on the vac slightly and stick something thin in the gap to reduce the suction.
I buy my ground foam ground cover and it is not cheap. When applying it, you always get some where you don't want it. I can just vacuum it up but that seemed wasteful. So, I built a scenery material trap. I got one of the empty 5 gallon cans from my home center and drilled two holes in the top that matches my vac hoses. I put the can in the middle of the large hose and small hose joint. I installed my vacuum reducer wedge under the vac lid to prevent collapsing the bucket (insert experience here), and now I have a ground foam pickup trap that catches almost all of the misplaced foam prior to it going into the main vac. I can reuse it elsewhere.
Do you use abrasive track cleaners? Rub one on your work bench sometime and see how much dust it creates. If you use one on your track, you should vacuum the right-of-way to get it up. Otherwise it sticks to wheels, it gets into turnout points, and it can cause both mechanical and electrical problems. Use the small hose on the vac to clear out the narrow gaps without endangering nearby people and pets.
A good vacuum is as important to layout building as any other tool in your arsenal.
