Nobody answered this yet?

Flies can be dunked in hydrostop as soon as you've tied them. They'll be good and dry before you go fishing. Frog fanny and bug float are usually applied just before you heave the flies into the water.

Usually you need to reapply the bug float or frog fanny after the flies are retrieved from a fishes mouth, or when you see the fly is no longer floating. Clean them off, dry them off, and re-apply the floatant. It's recommended you NOT use any other floatants on flies with CDC in them (I know ... controversy). For CDC flies use CDC oil SPARINGLY!