I try to wait at least 30-60 minutes. Lot depends how thick run is and reducer speed. Last thing you want to do is start sanding and find that it's not completely dry. Start with 1000, see how that works. You will have to rebase it anyway but you don't want too deep scratch to have to hide. Someone else might have additional advice that I haven't thought of.
i just recently had a run in my base.
i let it sit overnite as im using normal reducer in about 65 degree temps. i used 1200, although slow cutting i just worked it until it was gone. time and patience is better than having to reseal due to a break through