Yep can't agree enough.
I roller painted my old mini, and it worked a treat. I spent a good 4 or 5 days rubbing, sanding, and occasionally filling, each panel, down until it was perfectly smooth. Did it all by hand because I thought a grinder would be too fierce.
In the end, the paint I used was rustoleum, and there was a place I found online, that could mix it to whatever colour I wanted, (I used BMC tartan red), and delivered within a couple of days. I gave each panel about three coats, and left it 12 hours in between each coat, and then 18 hours after the final coat. It took a good 2-3 weeks after that to properly harden though, and that was in the middle of summer, back in 2008/9.
I'd love to paint my discovery sandglow if I had all the kit for it (the same as the camel trophy ones), but I'd be better off putting my efforts into setting her up properly first. If I ever do decide she needs a colour change, I'll be roller painting it, since a respray would cost the earth, and this is the way I would do it.