I mentioned this method as the one I use, back on page 1 of this thread, but since it's included in the 4wheeler test, I'll mention it again.
From the article:
"Slime Four-Way Valve Tool
How It Works: This tool ejects the valve core at a high rate of speed into the dirt if you are not careful. By the time you find the valve and wipe it clean you might be left with no air in the tire. Getting the valve core back in can be a challenge while the air is escaping.
Installation Notes: We simply pulled the valve core out and let the air out until we got to 10 psi. Without a secondary location to hook up a gauge though this is not always easy on the trail, but we found that escaping air changed pitch as the pressure got lower. We were surprised to find that this method was no faster than the ARB or Currie gauges, which we assumed caused some resistance.
Pros: Fast, dirt cheap, easy to transfer between vehicles.
Cons: Prone to losing valve cores, difficult to stop airing down at desired pressure.
Our Take: As cheap and simple as it gets if you are not picky about exact pressures, but remember to pack a few extra valve cores."
I've been doing it this way for at least 12 years. The tool cost about 2 bucks, like mentioned. I have NEVER lost a valve core in all that time, not even damaged one. Together with my $3.99 pressure gauge (the same one for 12 years) I get the job done, and done fast.
From the test, there's only 4 tested items that are faster, the cheapest of which is $29.95, and the most expensive is $149.95.
Versus $2.
I know some people gotta have the cool tools, but I'm very happy with my way.