Fire damage to my bowsprit!
As for the set up time for the epoxy, read the instructions since there are fast, medium and slow hardeners available and all are somewhat temperature sensitive. When you make the second set of kerfs, run them just into the cured sections to enhance the old-to-new bonding. A skill saw is what I would use to make the kerfs. It''s rip fence may not ride the rounded corner very well and you may need to clamp a board along side to help support and guide the saw. Good Luck, George.