Thanks for the suggestions!
I'm -always- forgetting to paint hatch undersides in the hull base colour. It doesn't help that some vehicles (such
as modern US ones) do have hatches painted in the interior colour!
I painted the cupola hatch green on both sides, but wasn't sure what colour the hull roof hatch would be; I'm assuming that the undersides were painted in the hull colour for camouflage/air visibility reasons, so I thought that since the hull hatch would rarely be opened during combat, it might be painted in the interior colour.
Still, this is one thing that's easily fixed, I'll repaint the hatch next time I do some painting!
I'll definitely have to try out some surface-roughening techniques the next time I build
a tank with cast parts.
As for things like track pattern, that's not usually the sort of thing I worry about - I add missing details and correct
very serious inaccuracies (i.e things like a hatch in completely the wrong position, not things like a hull 3mm too short!) if I can using scratchbuilding techniques. But as the tracks for this tank were vinyl (not easy to work with to say the least) and I didn't want to buy some AM tracks (which would probably cost more than the £9 I paid for the kit) I left them as they were.
Usually the method I use in painting tracks is first to paint them in an appropriate mud/dust colour (depending on theatre)
and then dry-brush heavily with gunmetal (Humbrol #53) so the mud stays in the crevices and the raised surfaces are metallic. Then I add rust, trying to avoid the raised surfaces as much as possible.
This final process didn't work so well on this model as the treads are so wide.
The paint I use for rust is Revell Matt #85, dry-brushed on with old paintbrushes of various size (heavily brushed on things like spare tracks and exhaust cylinders, lightly applied with a small brush to the hull corners and crevices)