Most silicone spray-can products recommend a safe distance to spray from, this may help evaporate most the light solvents. If you see wetting or dripping off your too close. Problem is, this distance will get you too much overspray when doing window and door seals.
I like the pump spray products (303, UV protect t-wax etc). I keep a small terry cloth wax sponge reserved in a ziplock just for this job. Wet the sponge and wipe the product on.
FWIW, I asked a CV boot manufacture about sprays, thier reply was just to keep them clean, wiped off with mild soap and water. Anything else would probably do more harm than good. Also that most automotive 'rubbers' are NOT rubber, so I assume many of the products that claim to protect rubber don't really do much.
[ June 13, 2006, 11:36 PM: Message edited by: wileyE ]