I have applied this several times and can concur that the stuff has to basically wear off your boat or hands and clothes rather than wash off.
best to apply in warmer water (another application in July or August when water is warm is fine) and when water is at full pool to help push it down into the cracks at the bottom.
Outside of that, I did the same you did, ordered way too much up front and then got to do 2 or 3 staged applications which I think was a good plan anyway.
I used a handcranked seed spreader but a solo cup or wide flat plastic bowl would be super too.
