Good luck and enjoy the work.

Q1: I just use a rag, just wipe it off until it feels clean. Normally the carriages come uninstalled. Be careful when you slide them on, so that you don't lose any of the balls.

Q2: I don't think there is a universal "best and only" solution. Depends on the situation, place, distance between and some other things. Use your imagination, test and correct if necessary. Spend as much time as needed, don't hurry because you will regret it.