It seems you have her on a trailer what makes cleaning them much less costly than one like me who has to fork out 300$ for travel lift and then aprox another 100$ for maintenance space.
However, interesting to know your experience as this would be a problem for many SKR equipped boats in a slip and also that SK recommend to not paint them what does not makes no sense.
The only thing what not should be painted are any parts what do retract, same as the ram's of trim tab pistons, but the rest of the non moving part?
Have you asked SK customer service about that?
Do you have a idea why the AF is not working? AF just to weak or get it washes away?
FYI i used first time the silicone based Airmar FoulFree on my transducers and get mixed results,
in 6 weeks i got one barnacle on B265LH transducer surface but the GT51M-TM was full of barnacles and my first guess is that the GT51M does not get enough water pressure on the upper parts to wash the barnacles away. So you may skip FoulFree, aslo as it seems it can become a nightmare to remove and no toher AF will stick to it if not removed 100%.
While the hull and the fairing block painted same day with International Trilux 33 was perfectly clean
Chris