Spymaster
Plastic Paddy
It depends how tight the fit is, which is why I prefer the idea of expanding foam.
I saw that one, but they revved the engine, didn't they (rapidly increased gas pressure = spud-gun effect)? An idling engine (say at lights, or stationary so it can super-soak you) should just choke up (at least it did the half dozen times I tried it on various mates ).
I don't think I've ever tried it, which is quite amazing given that it's one of those rite of passage things.
I will remedy this and report back.