I keep my boat in brackish water, so I get a lot of fouling and quite
a few barnacles on the metals.

I do haul for 3 months a year at present but the following may help.

I prefer ablatives and to me the 'secret' is to apply them SMOOTH.
Smooth will promote less surface adhesion of the fouling, and Ive
noticed that I dont have to paint quite as often .... as when I used a
'roller' as the sole means to apply. My choice now is Interlux Micron
Optima as it seems to be a little 'harder' than the previous versions
plus it has some biocide that in the first 1- 2 years helps to retard
the growth .... until it apparently leaches out and then you get only
the ablative effect.

How I apply ablatives so that they are smooth (I race my 'crab
crusher' so a smooth bottom is a plus for light wind sailing) but in
applying the stuff smooth Ive appreciated the 'other benefits' ...
longer lasting, easily drops the crud when at hull speed, etc.

With a roller apply on the first coat, let cure a bit and then with a
sharp chisel carefully 'lift' a small section to see if thats the mil
thickness I want. Let it fully cure - days.
Then with a orbiting sander knock the just the tops off the paint
pimples left by the roller - flat ... not much paint removed.
Then with a large polyethylene trowel ( the kind used in fairing a
'male' plug when fiberglassing) apply a large 'stripe' of paint with
the roller and immediately fair the wet paint with the trowel working
quickly and working towards the 'wet edge'. Clean the trowel as the
paint sticks or begins to dry on the trowel.
Leave a few inches of dry surface and begin the next 'stripe', until
all the way around the boat. Let these stripes cure and then go back
and fill in all between the stripes. This will begin to fill all the
valleys between the flat peaks that you sanded off.
Then at a different angle to the first set of stripes ..... repeat.
let cure. then repeat at a different angle, etc. until 'most' of the
surface is flat. Continue at those areas that arent flat using a
smaller trowel until the bottom is as smooth as a babys ass.

A smooth surface on ablative will quickly drop the growth off when the
boat is up to speed.

The following year instead of re-painting, I simply put on a quick
'trowel' coat to fill in the areas that have 'roughened'. I only
repaint when I see a different color of ablative showing through the
top coat. You dont want ablative to become too thick as if it
becomes 'thick' has the tendancy to come off in 'chunks'.


BARNACLES
For barnacles on underwater metals, I spray on Pettit 'zinc rich
barnacle barrier' - spray can. The result is that I get 99% less
barnacles on my running gear, throughhulls, and over the bottom paint
thats over any metal thats connected to the bonding system and zincs,
etc. If I dont get an occasional barnacle on those painted over
underwater metals ... then I check my bonding system for 'open shorts,
corrosion, etc. in the bond system'