Iíve been using Rust-Oleum Leak Seal which is very similar, but does not mention
any super hydrophobic properties. Itís a 1 part coating that results in a thin water proof
coating in either opaque or black. Itís very thin as it comes out of the nozzle and runs
easily on vertical surfaces, and may not fill any thing but tiny gaps in one coat.
If they would supply a nozzle that could be turned for vertical or horizontal spray
it would be easier to apply. Dries to a bit of a rubbery feel that might attract dust,
but seems to get smoother after being in the direct sun for a day or two.
They also sell a rubber/plastic spray for tool handles.
I used another similar flexible spray on my player piano bellows a number of years
ago, and itís still working perfectly.