I read some where that there is a tacky spray that can be used to keep grips tacky on baseball bats, and tennis racquets. It is designed to help against sweaty hands when playing in hot weather by not letting moisture soak into the grips, while keeping them tacky. If so, it might work on golf grips. I'd check with your local sporting goods store.

If not that then go with what the pros do. As LP42 posted, keep a dry towel handy to keep the moisture off your grips. Carry more than one glove(s), and change the wet one(s) out for dry one as needed. Most, if not all golf bags come with a rain, or travel hood, which can be used. If lost, a replacement can be purchased which is usually made out of clear plastic. An umbrella can be used if rain is the issue. If after all of the above has been utilized to no avail, I'd head for the 19th hole, and call it a day. GJS