The antifouling I use is "International" brand "Micron Extra" High Strength Self Polishing Antifouling...as on the tin.
Not cheap...AU$220 for 4 litres. But it did last years job and just got me through this job with only one coat, but managed two on the bunk areas. As you use it it tends to get quite thick and from my previous experience, must be brushed on.. When it is put on with a roller, there is a tendency for air bubbles to be captured underneath it...as it dries quite fast...and these will break and leave the hull exposed for growth.
David...She was in the river for the last 7/8 months...The growth along the waterline was even a bit thicker but I gave her a bit of a scrub...what I could reach with a scrubbing brush...a month ago.
Because this paint is " self cleaning" I might have got her clean on the mooring by swimming underneath, but getting a bit old for that caper.
I plan to be on the trailer for a couple of months, so will leave the second coat till just before she goes back on the mooring.
If the way this stuff sticks to my skin is any indication of how it bonds to the hull, AND I PUT IT ON PRETTY THICK...I'm not too worried about any wear and scuffing in future launchings. The trailer got its share too.
Miss U...dont worry about it coming off as a stain...its designed to slough off...the growth is not given a chance to be permanent...as it would on bare fibreglass..Next time to coat it, bung it on as thick as you like...the thicker the better.
It is not necessary to remove ALL the previous coating. If you are concerned about it, give it a water pressure clean.
Also, being on the trailer all the time, you could use the HARD SURFACE antifouling, designed for power [ faster] boats that live on a mooring...It prevents most of the growth but does not slough off...its mainly for high speed hulls.
A problem with contractors doing the job is that they spray it on...covers it so it looks good but much too thin...On a boat the size of a

, 4 litres should get you three good coats...use a fairly stiff, worn even, brush and scrub it on, not leaving a square inch...
If any other queries come up, I'll answer them as best I can...Puggsy