I use fast epoxy for all those little chores like cockpits, hatches etc. It's usually specified as cold weather epoxy by most manufacturers. It's not 5 or 10 min. stuff. Takes about 5 hours to set up hard but will get tacky in about a half hour. You can help it along with a hair dryer for all those wierd areas where gravity is against you as you described. Now you can pat it down with your finger, and it stays since it's tacky.

It's also great for all those areas where you don't have a good fillet and an air pocket keeps developing. Once it gets tacky, you push it into those corner areas and it stays. You could do this with regular epoxies except it's hard to judge when it will start getting tacky.