Ive had this pad brush for a while now. Is soft enough to take care of the pad and not harm it but at the same time cleans it thoroughly. I tried using the compressed air cleaning method as well but I dont particularly like it. Its pretty messy.
http://www.autogeek.net/padtool.html
As far as the temperature goes you should really have a good temperature when you start and yes claying is essential as we know. Ive started claying so much its not even funny. Those 2 hours extra give a much better and much much more long lasting result than without it. In extremes of temperature I would even recommend even having a infra red thermometer.
About the paint thickness gauge when it was just my cars and I knew what had been done on it I went by my judgement but when it come down to other cars I've realised that value of it immensely. Although these are extremely expensive I had the good luck of buying a second hand which was in pristine condition. Here is the one I have for now.
Defelsko Paint Thickness Gauge, Paint thickness meter, coating thickness gauge, auto paint meter, car paint meter
If you have the dough its a valuable addition to the arsenal. I would even rank it above buying a really expensive wax because if one ends up ruining the clear coat there's not much a wax can do, but thats just my 2 cents. 
