I did this to my mini when I had it. Posted a tutorial about it on a mini owners forum, and reposted it somewhere on this site too. It's fairly comprehensive. Covers, the preparation, type of rollers, paint, drying times, no. coats, etc. and has quite a few pics from start to finish.
I'm sure if you search around for it, you'll see it on one of the roller painting threads.
The paint I used, as recommended by all the VW, and mini forums, was Rustoleum combicolour. I can't quite remember the people I ordered it from, but they were fantastic. They mixed the paint I wanted, for little or no extra cost. I needed British Motor Corp. Tartan Red (So you could say tartan paint, does in fact exist

). Anyway, it was mixed, tinned up, and I received it within a few days, and at a very reasonable price.
It doesn't require primer, you just rub down, panel wipe, and roll it on. One of the problems with painting with foam rollers as is the norm, is that as you roll the paint on, you get air bubbles form which are impossible to eradicate. They dry and produce the 'orange peel' effect. Not noticeable from a metre or more away, but up close, it's very visible that's it's not a proper job. Having said that, it's more than adequate for a Landy, especially a series.
It takes a fair bit of patience, and the biggest tip I can give you, is give the paint a good couple of days after it's final coat, to cure before bolting the headlights back in, etc. Otherwise, you'll have soft paint being scratched away everywhere, and you'll get sticky fingerprints over the interior and windows, as you move about the vehicle touching it with slightly moist paint still.
Good luck.