Eric - you should look at the Personal Property Tax Lists - a listing of white males over 21 - that was taken every year in VA from 1782 on (like an every-year census, except 1808). Males were counted (and taxed) when they turned 16 - they were often named with their father paying the tax. I've had a lot of success solving just your questions by scrolling the PPTL microfilms. I have many of the VA county films on permanent loan at the Washington, DC FHC.
Good luck - Jim