Bottom job questions

Okay. The skiing is great, but I have not been sailing as much as I want to and I want to be prepared for early spring. I have a few minor leaks, chips around the centerboard box, hull discoloration of the white hull and generally want the boat to shine and am getting ambitious to complete a bottom job on my 21 SE. I have a lot of epoxy glass experience building cedar canoes and refinishing an older Tornado cat, but not much polyester or gel coat experience. I think I have read all articles on this forum, watched J's videos, but I still have a few questions that hopefully some of you can answer.
- What is best product and/or method to build up larger chips on edges of centerboard trunk?
- How much gelcoat to cover both 21' hulls below deck edge?
- How temperature sensitive is the gelcoat? It is almost always 50 degrees in the northwest. Are there methods (additives) to accomodate the lower temps?
- How many gelcoat coats for bottom typically?
- how many caots on the sides typically?
- What are the biggest most common mistakes made when applying or finishing gelcoat?
- Other recommendations?

Thanks!!!