On the topic of front sight tools, like Smellie posted cut the tip off a screwdriver and saw a slot. The Brits made it a reverse screwhead, so ordinary soldiers couldn't change zeros. The other tool is a gear or windshield wiper arm puller. Once you have loosened the screw, you need to nudge the sight leftish or rightish. Fumble fingers and hammer taps are unscientific.
The business of gauges is a overly cautious. I doubt very many CGN members have more than one headspace gauge, never mind one for each gun. No.4s are a special case because of the removeable bolt head, but it is almost a nonproblem. If the bolt won't close on an empty chamber, turn the bolt head one revolution and try again. If it spits brass or shows signs, get a smaller number bolt head (I think smaller is tighter ....).