sandblaster or wire brush + rust neutralizer?

Do you have bad through rust holes? Sandblasting can work and warp sheet metal if done incorrectly plus the sand/media gets everywhere and you need a large air compressor to use one. POR-15 is great, but fixing the holes would be paramount. Depending on what you have planed for the car and how much you intend to do, you can just patch in pieces of metal to fill the holes. Eastwood sells an epoxy kit that requires no welding. Post some pics, folks might have some better ideas if they can see your specific issues.