waterproofing exterior brick

I am also assuming you are referring to Siloxane. Anytime I have used Siloxane I have purchased it as a clear sealer - I'm not familiar with a paint that has Siloxane as a component - then again there is a LOT of stuff out there I am not familiar with. Siloxane sealers are pretty easy to work with. They are pretty thin and easy to spread - not really any different than working with any other masonry sealer. Exactly what are you looking to do? Are you getting water seeping through brick? Above grade, below grade?? Do you want to paint it a solid color? Have you looked at products like Thorocoat and/or Thorolastic? Not sure where you are located but Insl-x (Which is a division of Ben Moore) does make Siloxane - runs @ $40 a gallon and any Ben Moore store should be able to get it for you.

Hope that helps some