Hey Bish, I'm looking in on this for the first time and it looks like you've got it all under control. Great job so far. Good call on lightening the paint on the top--a little bit of "scale effect" really helps a paint job in my opinion. :)
As far as the filters go, you really have to understand that filters are meant for VERY subtle shifts in the tone of a color. You won't get the same kind of tonal shift that you would get in, say, an airbrush lighter base color. However, if you were to modulate the color the way I usually paint mine and THEN use a filter, you would be able to effect a very slight color difference over the lighter shades, Filters tend to work better over lighter shades, in my experience. German gray takes a blue filter very nicely, but I don't know what exactly that AK Filter is based uponm color-wise.
I also believe that most 1/35 figures are a hair larger than true scale. I have a very hard time fitting them inside almost any given model.