Just to play the devils advocate
I would suggest just sticking to the Gamesworkshop spray.
As long as your not pulverising the models with paint at a range of 5cm it is never bad.
They are expensive yes but they have always given me a nice coat, they are compatible with every other range of potted paint ( you won't have to worry about separation or paint not bonding to the primer).
They now have several colours that are really great bases for pretty much any paint scheme and if you do want to strip them the GW spray does come off when stripped but you will have to use a toothbrush to scrub the models and a toothpick to get some of the paint out of recesses.
My recommendation is that you use the mournfang brown spray. Dark colours work well on it and building from light brown to white/light colours is also really easy.
As an example my orks are all undercoated brown and with only two layers there skin is bright as,
here is an link to them. http://www.westgamer.com/forum/viewtopi ... 61#p437261
Alternativly if you want something quite light go for the ushabti bone, I would use this over the skull white spray as it is much less forgiving that the white if you miss bits, and it looks great with any wash.
I noticed that people are recommending Dettol to strip your models, as your a newbie I would advise you NOT to do this, go with the safer simply green option, Dettol is fabulous for stripping metal models but if you use it on plastic you can melt features.
Simply green on the other hand will strip everything of plastic given time and there is no chance that the plastic will be melted or go flimsy
If you do use Dettol only leave the models in it for a few hours then scrub and see how they are going, better safe than sorry.
On the other hand I left some space marines in simply green for 6 months and everything came straight off and other than discolouration the plastic was completely fine.
goodluck and don't forget to start a hobby blog so we can see how your going