Because a clean sandblasted surface (using fresh sand, not recycled sand) is the ideal surface for adhesion with RustSeal and can be prone to surface rust with an application of RustBlast, we recommend applying RustSeal directly to a sandblasted surface. Please be sure to wear gloves when handling the sandblasted piece to prevent finger oils from getting on the surface.
With that said, you can apply RustBlast to a sandblasted surface before applying RustSeal, but please be aware that that surface will be more prone to surface rusting if not dried immediately after rinsing the RustBlast off the surface.
Please be sure to check out the complete directions for RustSeal HERE.