I like to clear coat the final paint with Future, then use oils or enamels for the wash.
Make sure you use a wash that won't dissolve the paint it's sitting on - never paint your final coat with enamels then do a wash straight onto this with enamels - you'll just end up wiping the final coat off the surface.
Future seems to create a barrier that is impervious to oils or enamels. Otherwise you pretty much have the right idea.
Try looking in the painting forum - there'll be heaps of posts about washes there. Maybe try the search function - that should be a help.
Cheers,
LeeTree