Home Depot. Plasti dips website has a list of retailers. Dipyourcar will have the largest color selection I believe though.
It's very easy! I can't remember where I read it, but Plastidip is supposedly formulated to "re-melt/liquify" itself when sprayed on a dry coat. This allows it to basically never cause drips.
You can order from DipYourCar through Amazon http://www.amazon.com/gp/browse.html?ie=UTF8&marketplaceID=ATVPDKIKX0DER&me=AZFQ68FCQXH6V
Basic colors (Red, Black, and White) can be found in most department/hardware stores. MAPerformace has blaze colors in stock now I think too.