Yes, I've tried it. Works OK, however, with hydro2 needing to be applied wet its not the easiest to apply without wetting the inside of the helmet.
Another alternative for this is a product called gtechniq g5, which is a very similar product, although classed as a glass sealant (its actually more durable than hydro2 and slightly more hydrophobic), its applied dry via an applicator pad (like a makeup pad :o) then buffed off, safe to use on the helmet and durable for 3-4 months.
Gtechniq g1 is another "glass sealant" which is durable for around a year, but not safe for visors as far as I'm aware.
Another alternative for this is a product called gtechniq g5, which is a very similar product, although classed as a glass sealant (its actually more durable than hydro2 and slightly more hydrophobic), its applied dry via an applicator pad (like a makeup pad :o) then buffed off, safe to use on the helmet and durable for 3-4 months.
Gtechniq g1 is another "glass sealant" which is durable for around a year, but not safe for visors as far as I'm aware.