I've played around with the idea of practicing with airsoft and a shot timer. I've got a cheap plastic spring-air Sig 226 replica, and a handful of XD holsters that I'm not going to use for anything else. The Airsoft fits the XD holsters well.
The first problem is that airsoft is nowhere near loud enough to trigger the shot timer. However, the timer can pick up the sound of the pellet hitting cardboard if the timer is close enough. Clipped to the back of the cardboard turns out to be close enough...
This leaves a second problem--The normal time between pressing the button and when the buzzer goes off isn't long enough to get to the "firing line" and positioned.
This is solved by using "par mode". I'm not sure exactly what it is meant to be used for (the instructions said it is rarely used anymore) but it gives a second beep, and measures the time after that. By setting the par time to 3 or so seconds, I get a total of 5 seconds to get positioned.
On the Pact Club Timer, modes are set by pressing both arrow buttons at once. One of the arrows sets the mode to instant, the other to delay. The next selection is "par time" mode--press the "go" button now if you don't want a par time. If you do want a par time, the arrow keys adjust the digit you are on, the "rvw" button moves to the next digit. I had to look this up, and it was harder than it should be to find--PACT doesn't appear to have the instructions on their website.
I'm more than likely going to make a proper pellet trap, rather than just a piece of folded cardboard. I'm also going to make it so I can use a semiauto bb gun, with protection for the timer--one drawback to the springair is that there's no way to do a doubletap. I'm also going to try to figure a way to push the go button remotely, without disassembling the timer.