how clean does my suspension need to be before painting with Mastercoat?

[hpcgmc]

I had my A arms and most of my smaller front suspension parts sandblasted by a friend at his work. He works for the county and happens to have access to a sandblaster, but has not used it much, other then for my parts.

He cleaned things up alot, then I hit it with a wire wheel on my angle grinder. I plan to go over it with wax and grease cleaner, then paint with Mastercoat. I've never done much painting, so want to make sure I'm not missing something. Do I need to go over everything with sand paper, or a wire wheel or something, to make the paint stick?

Here's a pic of an upper and lower a arm that I'm hoping is ready for paint.

Thanks!