hi! i've used certain-dri for about 5-6 years now, and it works great for me. just put it on at night, but like you said don't wear anything fancy that may be stained, although i've never had a bad experience. no, you don't have to wash it off in the morning either-it won't stain your clothes after that long of a duration after the application. it may burn a little for the first few times you use it, so i totally don't shave before i put it on. for a while, you will probably have to use it every night, then you can taper off and do every other or every three nights. i still use a regular anti-perspirant/deodorant, just because it makes ya smell nice
the certain-dri doesn't have an odor to make ya smell good, so i would still use at least a deodorant so you don't have "pit" smell,lol. also, try using an anti-bacterial soap on your armpits, i think i used to use dial, and it will help kill the bacteria/smell too.
good luck, it's worked wonders for me