Some good advice above, but let me add a couple of things (I've been painting since 1966, taught auto body repair and paint in a local high school for 10 years, and still paint for a local body shop occasionally). If you want to get your paint locally so you can have access to a paint professional, find a local dealer that sells DuPont Chromabase (Do NOT use DuPont Nason brand) or Matrix System basecoat color. Both mix one part paint to one part reactive reducer, so that makes getting proportions correct very easy, and both dry very quickly which reduces the occurrence of "runs". I haven't used Summit's paint, but it looks good in the pics above and I've seen Jim's work; if he says it's good, it's good. Compare pricing between DuPont or Matrix and Summit.
For clear I like 5-Star Extreme Clear, but I have used other brands (Ditzler, DuPont, Silver Sails, Matrix, etc.) All the Urethane clears
spray similarly, but some "build" faster than others. Look for the term "high solids" on the label. Clears don't all mix at the same ratio, either, so pay attention to mixing instructions. The clear should come with a hardener/catalyst in a separate container. If the temperature where you're spraying is above 85 degrees, get
Slow hardener; if the temp is below 85, but above 60, get Medium; if it's below 60 degrees, get
Fast hardener. Take your time spraying the clear and allow ample "flash time" between coats or you'll find yourself sanding and buffing a bunch of runs...
Get a proper spray mask with correct filters at your local automotive paint store. DO NOT spray automotive paint with just a dust particle mask or a cheap mask from the local hardware store that sells house paint. Isocyanate hardeners contain Cyanide - that's the same stuff used in the Texas gas chamber! Prolonged exposure to Isocyanates can cause permanent nerve damage.
As for wetting the floor... If you have a small confined space (small one-car garage) with poor ventilation to paint in you may NOT want to wet the floor for the reasons 409T said above. However, if you are spraying in a large, well-ventilated area you can lightly wet the area immediately under and around the car so the air stream from your paint gun won't stir up the dust from the floor. If the area is well-ventilated and the air is kept moving, just damping the floor will not raise the ambient humidity appreciably. When I paint in my home (2-car) garage I dampen the floor under the car, open the screened windows, and set a fan under the partially opened overhead door to pull air out.
One last tip - don't paint in your home garage at night or your paint work will be a graveyard for bugs! The light attracts them and the fumes kill them... just as they're flying over your freshly sprayed surface!