I usually wash the areas I want darkened. If I go overall, then I have to drybrush overall, and some areas just aren't worth the effort (for me at least)
I've never tried the soapy water method. How do you apply it? what kinds of things to watch out for? How to clean excess>
Hehe, as for the future question, read this issue of FSM. It's got an article JUST on that. They reccomment the following ratios for the listed results. Keep in mind, these are overcoats (I assume):
1 part flat base to 3 parts future = dead flat
1 part flat base to 10 parts future = flat
1 part flat base to 15 parts future = satin