icebones,
The way a gunsmith showed me to check the timing quickly was to cock the gun SA and watch as the cylinder stop goes into the cut out. The stop should drop into the cut out with no drag on the cylinder.
To see if the cylinder locks up correctly, first see if there is any front to back play. You can sometimes budge the cylinder, but if there is movement, real play, do not buy the gun. Look to see if the cylinder gap is even. If it uneven from top to bottom, pass it up. Cock the gun SA and let the hammer down slowly. Hold it there and move the cylinder left to right. Smiths and Rugers should have very little play. Colts should lock up tight. Also, look at the gun from the front. Push gently on the cylinder as if you were trying to open it. If a gap opens up between the crane and the frame check it closely. Some wear and a small gap is okay, but a loose fit and a big gap is no good.
I once checked out a snubby that had a cylinder that could be be pushed out from the back about 1/8" on one chamber...so push gently on the cylinder from the rear, too, on every chamber when cocked.
Also, check out the revolver buying/check out guide at the top of the revolver page. The FIRST things that I look at are the screws. If the screws have been boogered up by a home gunsmithing job, I look no further.