Air cannon/spud gun trigger

I've opted to go for the modded sprinkler valve trigger.

My questions are thus:

Where can I find the required 'blow gun'?
What is the 'blow gun' for when not killing potatoes?

Will the valve reseal if the trigger is released before all the pressure in the tank is gone?

So, can you fire more than once before pumping up again?

The blowgun in question is an accessory for air compressors, and can be found in the air tools section of any hardware/home improvement store. They are used at the end of a compressor hose to blow sawdust off of workbenches or your clothes, or whatever.

You will need to repressurize your spud gun for every shot, as the sprinkler valve will dump all the air in your pressure chamber, even if you just tap the trigger.