This forum is full of experts and I am just a hack at painting, but here is my 2 drachmas:
For hull and topsides, don't sandblast -- if the paint that is on there is sticking (and the original Marinette paint is really on there) then sand with 36 grit, cover with high-build epoxy primer, sand with 100 then 220, and then roll on a good topside enamel, three thin coats scratched with Scotch pads between coats. I have used both Interlux Brightside and Petit Easypoxy. I prefer the latter, but the brightside is easier to brush in inside corners where the roller won't reach.
There will likely be cracks in the filler that the primer won't handle. Use WEST epoxy with microballoons as fill and sand excess off with 36 grit, before putting on the primer.
Watch out for advice from guys like FastJeff and Jralbert. These guys are professionals, they paint cars, they put on a finish that looks like it was done by Mercedes.
Listen instead to Slow Doug: your boat is not going into a show, if you try to do their level of work you will never finish. Roll, roll, roll your boat, and then get out on the water! Don't forget the beer.
1975 32' Flybridge Sedan, twin Perkins 6-354 diesels, 1:1.53 velvetdrives, 16 X 19 props. Merritt Island, Florida