I wouldnt recommend shot blasting the frame,as has been said it will most definately pit the surface and could put holes in your frame,if any type of media blasting was to be used id say a very fine glass ball peen with high powered water.
Also ive heard different things when it comes to using nitromors on Aluminium,as its a porous metal it could soak into the metal structure and therefore either keep damaging the metal or render any paint/lacquer you apply on top useless,i didnt have this problem myself but i have heard it said before.