Hey there Coz,
My best advice is to find one or two good paint supply stores in your area and go in and talk to the folks there. The people in the supply shops in my experience have been very helpful and will steer you in the right direction. They want you to do well so you buy more stuff from them. You can also go to them with any problems and even bring anything in that you are having an issue with for firt hand info.
In my experience using HOK for example I end up getting a price within a couple of dollars of the mail order stores at the shops I go to because I don't have to pay shipping. I'd rather spend $2 or $3 more for a quart of paint instead of having to wait for it.
I've also been lucky enough to have a few painters invite me into their shops to watch them paint when they found out I was new and heard me asking the supply shop folks questions about paint and what not.
If you want to get smaller quantities on line I know that a lot of people use
https://www.coastairbrush.com/categories.asp?cat=11
Good luck.
AJ
