The paint brush works great too - just apply it lightly and don't forget- like he mentioned- to peel the tape off when gel
Why not just put a vinyl surf sticker over it?? It would be much easier ... That's usually what I do. Actually I got this vinyl tape that I found at the hardware store meant for windows(glass) that works great and it's clear! When I go on surf trips- forget carrying a ding repair kit or resin- I just bring the tape! I have temporarly repaired some fairly big dings with it - with no issues!
Yeah, but eventually that sticker or tape is going to come off or have a higher incidence of failure than a proper repair job. What's if it's a "magic" board? Just like a car if you maintain a surfboard by fixing any problems that arise properly they can potentially last a lifetime. Although, in my mind after a major repair, they never seem to ride the same.
On the subject of dams, I keep a roll of wax paper in my ding/shaping kit for bigger jobs that stuff is essential, but for little jobs I like to fold a piece of tape over itself and make kind of a ridge. As long as it's at the right angle excess resin just drips right on to the floor. Shaping stands really make a world of difference when doing even small repairs. Cheap and easy to make too. Any surfer with the storage space and the inclination to fix their own dings should think about making a pair.
The wax paper worked well, not quite as good as the acetate paper though. The rigidity of the acetate paper is better at holding the edge and requires less sanding. Flat spells are good for something-if it lasts too long might be finding dings that aren't there.