Painting

I am thinking about doing the paint job myself because I have done it before but I am concerned about dust and bugs in the garage. As well, I gather that before soon, everybody will have to use water based paint..which requires special equipment. I was thinking about getting my materials before that law came in..

I have a sanding question. Once you have a coat of poly surfacer or primer down you start spraying a different colour on questional parts to make sure the body is flat. I read that you shouldn't use rattlecan paint because it willl clog your sandpaper. If you are taking a day to do the sanding, how long would the normal mixed paint in the can stay good and not foul up the sprayer.. or woud a rattlecan of custom car colour act differently.

Thanks
Ian.