I would imagine they should be reusable so long as you take them apart carefully (that goes for pretty much everything you take apart).
As for tips on disassembling the car, I guess more info is needed. Is this a respray the same color? Do the jambs and edges need to be done?? Lots of different ways it can go down. For instance, just a respray - you can leave the fenders and such on, but I'd take the front header panel out, front and rear fillers, etc etc. Basically anything that "bolts up" to something and doesn't have a "jamb" or gap needs to come off (this includes the glass, to do it right - but some painters can do a good job "roping" or masking the glasses and such. Again, just depends on how in-depth your painter is planning to go for your particular job.