I have not used the Prop Speed but this might be a cheaper option. I spray the prop and shaft with Trilux anti foul paint that is designed for aluminum outdrives on power boats and it seems to work very well. I rough up the surface with a Scotch Brite pad and then prime with that yellow zinc chromate and then a couple of coats of the Trilux. 2+ years and no barnacles (or anything else) here in the PNW (cold water). About $20 for a can of it, a little less for the primer. Obviously, you don't paint the zincs.
SV Laurie Anne
1988 Brewer 40 Pilothouse