I've had a Rawlplug foam gun for a couple of months and only got
around to using it properly today (I'd ****ed around with one
previously, but not for long).
By 'eck, it will pay for itself in the long term - I will have a need
for many cans of foam over the next year or two and the gun makes the
bead of foam so much more controllable and as big/small as you like -
also puts it exactly where you want it.