Plastic polishes can be found at auto stores and aquarium stores. If there is resistance between the base and the work errors can happen very fast. Carbide bits are preferred as the bits take much punishment. Bits with guide bearings are best for portable work. Helical straight bits will give superior cuts.
Bits can be sharpened on a diamond stone, only the flat part is sharpened.
Accurate depth settings can easily be made by using a drill bit of the appropriate thickness, either between the depth post and stop on plunge routers or, using two bits between the base and the work on fixed base routers. Clamp a straight edge onto the work, square and close to the edge. Then using the straight edge as a guide for the pilot, rout it off. Stop just before the end and finish of the opposite direction to prevent tearout. So I will conclude this part with a few notes.