I used a long piece of old trans cooler line, attached it to my blow gun via a rubber hose, and about 40 psi I cleaned out approx 20 lbs of sand, silt, crap, etc from my frame rails on my 74 Monaco Police car during the resto......and ran / sprayed primer and paint in as best I could ...the trans line worked great, using the end to scrape away at the inside corners and get the packed silt...but do it outside trust me