sandblaster or wire brush + rust neutralizer?

I love the One Step rust ender. It's pricey at 40 per gallon but... It can be applied with a brush, a mop, a sponge, a pump spray bottle, lawn and garden sprayer, whatever. Eco-friendly product made from acorns. Completely harmless and cleans up with warm soapy water. Not many products can make these claims.
For areas like inside the cowl, between the rear quarters and trunk floor extensions, I have a little 'Y' shaped tube that siphons the stuff out of the jug and dispenses with compressed air nozzle. I blow in one opening until the stuff drips out the other.