Not necessarily, but you get a better bond if you bead blast first. This gives the metal a "tooth" for the coating to bond to and increases durability.
However, you can get an excellent job as long as you get the metal totally clean.
Brownell's sell Aluma-Hyde II which requires no baking and air cures to a durable finish.
When cleaning, be wary of using any of the super strong liquid cleaners like Simply Green or Greased Lightning. These will attack aluminum and can do serious damage rather quickly.
If you consider bead blasting, be very careful about the blaster setup. If it's been used to blast carbon steel, like car parts, the pressure will embed tiny particles of steel into the aluminum and the carbon steel can rust later, ruining the surface.
I once had a custom who bead blasted an aluminum pistol frame in a garage blaster and was astounded when his aluminum gun started rusting.
So, if you do a good prep and clean job, the Brownell's aluminum finish will do a very nice job as long as you do yours.
