i am one of the few that lightens the base coat first.
i feel it gives me a bit more leeway to use an overall wash w/o darkening the kit too much.
i don't think i am 'right' it's just what i am comfortable w/.
you will find your own favorite way too.
i am w/ the guys on the washes - but a word of warning!
if you are not familiar w/ washes - search the forum on the topic as it comes up quite a bit.
the thing to make sure of is that you use a was that is a different TYPE from your base coat.
so you can use an oil wash over acrylics, or an acrylic wash over enamel, or a water
thinned wash over most anything.
but you don't want to put a wash that is 95% Tamiya Acrylic thinner down over Tamiya Acrylic paint!
the results are somewhat predictable! hello bare plastic!
there are some who say they 'do it all the time; just let the paint cure'
but not for me, thanks!
i use water-colors over my acrylics, a lot of guys use oils.
if you decide on water colors,
put in a drop of dish soap to break the water's surface tension and help flow.