1. how much concentrated must be isopropyl alcohol on cleaning the FL without doing any damages.
2. I came across astroglide liquid glycerin and paraben free. Is it good for FL ? I dont want to have any allergies on applying the lubricant. I would like a safe lubricant.
Yes Isopropyl (as stated on their website & instructions) should be used to clean your fleshlight, only occasionally to re freshen. I do mine about once a month with alcohol. Use it neat then rinse well, it doesn't need diluting as it only is produced at one strength.
Sex toy cleaners are normaly ok, check they are soap free though, water is really all you need though.
Drying the bugger is the tricky part, wash & rinse, I normally drag a clean towel into it before leaving to air, they soon smell if put away wet.
A bit of corn startch powder (bought in all sex shops) stops them feeling tacky & more like skin!