I wanted easy rust, so I picked up this off Amazon for $12:
Paint on the metal paint, let dry, then paint on the acid glaze and wait. Easy enough...
The metal paint goes on about a mid tone grey, hard to see in these pics but nothing exciting
Here's the acid glaze, just looks wet...
Next morning the change was slight, so I hit it again and got this:
I don't like it on the surface panel, but it's not bad in the cracks on the lower part. I think the trick is put the paint and the glaze on relativitly thick. I'll try a combined arms approach today and see how it looks with all the ideas combined.