If I were to paint my tracks, and on trucks on the loco, would this disrupt the electrical connection between the two?
If you paint the rails, you need to clean off the top and insides of the railhead to allow for conductivity. If you paint / weather the truck sideframes that wouldn't affect the electrical connections, but if you paint the wheels you'd want to be sure the tread - the part that touches the rail - is clean.
You can use Neo-Lube from Micro-Mark's catalogue which is an electronics lubricant that dries to a flat dull gray. Even though it does conduct electricity, you'd still want to clean it off the tops of the rails etc. since real track looks that way.