Andras,
Bad idea: Spraying into a box to catch overspray is doing nothing more than concentrating organic vapors into one area and increasing the potential for overexposure to organic solvents through inhalation. In lieu of a spray booth:
1. Spray outside.
2. If you need to spray inside, stay away from rattle cans, and try to use your airbrush exclusively. Throw the "overspryay catcher" box away, and open the window (If you're from Florida, this should not present too much of a problem even in the wintertime.). Position a room fan behind you and at a slight angle to your work area. This will create some cross-drafting, will blow generated vapors out of your breathing zone, and with an open window will help dilute any organic vapor concentrations. Make sure you leave the room door open to help move as much fresh air as possible.
Next, get yourself a good respirator. It should include a silicone/rubber half mask with organic vapor cartridges and paint pigment prefilters. Normally, hardware stores stock a variety of these things in kit form, so you don't have to go hunting for the right components. They are worth the $20-$25 dollars you'll spend for them. Keep your respirator clean and cartridges fresh by storing them in a plastic bag when not in use.
Use the absolute minimum amounts of paint and thinner to get the job done. Try using the color cup instead of the bottle (if so equipped) to do your spraying. Don't leave solvent-saturated rags, paper, etc. lying about after use. Take them outside and throw 'em away as soon as you can. Keep paint, glue, thinner, and other solvent-related products capped when not in use. Wear nitrile or latex (if you're not allergic) gloves to avoid excessive skin contact/absorption.
Lastly, something to remember: Just because you can smell organic vapors doesn't mean you are being overexposed to them. Most organic solvents (there are exceptions of course) have odor thresholds that are significant orders of magnitude less than what it would take for you to be overexposed; however, taking a few precautionary steps as mentioned above should keep you pretty safe.
If you have any additional questions along these lines I can help you with, please feel free to shoot me an e-mail.
Hope this helps some.
Gip Winecoff