Pre-shading with a black sharpie?

Sharpies can be used for this, but when I have used them I have noted that they have a different look in the ink they lay down from paint. Hard to describe but it is shiny, a bit transparent, just a bit odd looking. If you got it down dark and applied a dull coat after it might make that appearance go away.

tank -

Yes, it does work, but you just don't bet as much of a feathered effect as with the spray. I've used with with flat paints and have had no problems.

Archer out.

I've tried it, works, but like rkoenn says, it dries shiny so you need to flatten or gloss it to match your utlitmate paint finish. works great for Gundam robot models post paint too.

I've tried using sharpies on road wheels for tanks, and it does look transparent and a little glossy. might have to try it on Gundam models....