I'd say you're doing it right. Aside from being able to reach, and weld prep ALL surfaces being welded. If possible, wire brush as much as you can, blow as much debris out that you can reach with compressed air. Maybe fabricate an "extension hose" attachment to your air gun to reach into tight spaces to blow out the "crap", and wipe, or flush with acetone. **Always evaporate the acetone with air, and make sure that the fumes are ventilated before striking an arc!** You can also try running a propane torch along the weld seam to burn off contaminants, inside and out, then wire brush again.
