checking gauges questions

[beautimus]

okay, heres the deal. i have restored one gauge cluster,(paint, new lens and bezel), but i want to do a really good job on this second one. i would like to bench test everything before i tear the cluster down.
heres the first question. i assume (please chime in and correct me if i am wrong here) that the gas gauge, and the battery gauge are like amp meters.
so, can i check the gas and battery gauge by putting a potentiometer in the middle of a piece of wire and hooking that to the positive side of a 12 volt battery? if so what range potentiometer would i be looking for? i am pretty sure that i can use a fuel level sender to check the gas gauge, but not sure if that would work for the battery gauge.
i plan to use my air tank to put pressure on the oil gauge to check it at 60, 30, and 10 psi, do you think that will work?
i don't have a clue how to bench test a tachometer, any suggestions? i will test the speedo by hooking it up in my van and taking it for a short spin around the block. (disconnect the van speedo, hook the cable to the cluster i want to test and prop it up in the floor of the van, and drive it.)
any helpful suggestions would be appreciated.
thanks, tony