I usually paint track pieces separately. I put them on double sided tape on a bit of board. I spray with Citadel Black and then Tamiya or Mr Colour Gunmetal.
The vehicles are undercoated in Citadel Black, then Tamiya Light Sand. The tracks get glued on, then I go over them with paint markers for weathering. Silver paint marker for wear and tear, and various mud and dust colours for dirt. It's not precise, and it won't win any modelling prizes, but it's good enough for the table top.
When I was building these kits, I accidentally dropped one of the guns, breaking the resin in a couple of places. Luckily I found a couple of the small fragments and glued them back on. Superglue (cyanoacrylate) adheres to resin very quickly, which is tricky if you are trying to adjust the placement of pieces on a model, but it is a very strong bond. Once painted, the join is hardly visible. I couldn't be bothered repairing the handle on the breech, because I expected it would just break off again during game play.