Have a word with Jon (the guy who is running the tale of x painters warhammer campaign) I know he's dabbled with it.
Hi Niel.
Army Painter stuff is good, but not cheap.
I've had a crack and they're good. In my opinion, the dip is excellent, and I certainly wouldn't try using any of the cheaper alternatives or home-brews instead, its worth the money.
The matt varnish I would also recommend. I've never had any problems with it, I don't find it dulls down my models too much, and its a good protector. If you are dipping models, you will ABSOLUTELY have to matt varnish the models after dipping, as it adds a varnished shine to your models which looks horrible.
As for the coloured primer, I wouldn't bother. I know a few people who've had success with halfords car spray, much cheaper, although you'll find it may have a glossy or satin finish that more paint won't stick too. A friend of mine did a Chaos Warrior army very quickly, using silver car spray, followed by a light matt varnish (so paint will stick to the model again), highlighting details in gold, boots in brown, skin with skintone, followed by dip, and another coat of the matt varnish..... I can honestly say they were better than most people can do properly.
My best piece of advice with dipping is to percevere- your models will look absolutely awful after every step, until they finally get matt varnished and based, at which point I promise they'll look great. Don't get disheartened by how bad they look before you finish them, keep going and see what it turns out like, you'll be surprised.
Also- brush on the dip. It saves money, and saves yourself from bad elbows from all that shaking.... the stuff is horrible, you don't want it flying everywhere. I've heard of people attaching their models to power drills, dipping them head first into the dip pot, then turning it on to "shake" off the dip..... the mess must have been appalling.... just dont go there!