We have been using the Interlux Pacifica Plus. It's a non-copper, biocide paint. We get about 2 seasons out of a bottom job in the Northeast if we stay in the water and slightly less if we are out of the water due to the photodegradation of some of the biocide chemicals.
We have 2 layers of Interlux Interprotect barrier coat as a primer for the bottom paint (with the type of hull we have on our C310s we don't have to worry about blisters). We did a complete bottom job in 2012. Took it down to gelcoat. Put on two coats of the barrier coat and then "hot coated" the first layer of bottom paint (applied while the barrier coat was still tacky). We applied two coats of paint over the entire bottom and 5 coats at the water line (about 18" wide strip from the top of the waterline down). Last year we sanded off the bottom paint with 220 grit and then reapplied the bottom paint (same paint). Again, two coats of paint over the entire bottom and 5 coats at the water line. Both times we painted the bottom like I described above it took 2 gallons of paint. We would even have a small amount left to do as many coats as possible on the bottom of the keel once we were on the lift ready for launch. I slip the yard guys a couple of bucks to put us on the lift at night before they leave and then not launch us until the morning. This way I can get the areas where the stands were and the bottom of the keel good.
We did the barrier coat in gray and use blue bottom paint. This gives contrasting colors so it is easy to know when to stop sanding or when your bottom paint is wearing away.
We use the foam rollers over the nap rollers. The best are the actual epoxy rollers but they are more pricey. This gives multiple thin coats that appears to give better performance when you include regular bottom cleaning. (I say appears because I haven't done anything qualitative to document this but it was a type from a top notch fiberglass guy and qualitatively appears to work)
Up here growth is a little slow prior to late May, early June because of the cold water temp. But starting in June I typically clean the water line every couple of weeks and the whole bottom monthly. I do this by swimming at anchor in a couple of our favorite spots and using a soft brush. Takes about 30 minutes to do the waterline and about 1-2 hours to do the whole bottom depending on how my lungs are doing with holding my breath.
With this practice I didn't see any gray from the barrier coat the first year. The second year I started to see some gray swirls in August. By October when it got too cold for me to swim without a wetsuit I could see some pretty big gray areas. I also had to use a green 3M pad on a couple of tough areas of grassy growth that looked like a beard at the water line. I never got any hard barnacle growth except on the prop and shaft. I would get a little bit of slime on the bottom but it came free with little effort.
I attached some photos of the bottom job at launch in 2012 and then after 2 seasons.
Hope this helps.
Fair winds,
Jesse
