[Jonny042]

So you're doing a colour change? I assume you'll strip the topside with stripper?

You might re-think the need to strip the stonegaurd, at least on the entire car - depends how far you want to go. You could paint the blue over with the orange after cleaning it well with lacquer thinner and a brush. The blue is likely pretty thin in most places.

Of course in the places you do want to strip you are on the right track.

I've had good luck with the wire brush on the 4" grinder. You'll need the knotted/wound kind, and you might go through a few of them. Can Tire has them in a few diameters, and the smallest is handy for some of the tight spots. Messy and noisy.

If you are careful you can leave the factory applied electrostatic primer (black) behind. In the spots you break through that you'll see the galvanizing but you won't remove is all until you press even harder.

Even if you remove all the galvanizing via media blast, it's still going to remain where it's doing the most good, in the places you can't get at or see.