A needle gun from Harbor freight will work pretty good for frame stuff. It knocks off the loose stuff good, we used them all the time onboard ship to de rust. If you have a pretty good compressoir, I have used mine on frame parts and rear end and such, does a pretty good job - just makes a hell of a rackit. I got mine from Harbor freight, have to say its worked pretty good - had it about 3 years now, good luck.
