When inflating the seat chambers and the footrest I had a lot of trouble preventing air from escaping before I could plug the hole. Is there a trick to do this without having to try and re-try for a zillion times? I tried with the foot pump and it's really difficult. Once those are inflated it's really easy to inflate the main chambers.
I realize that these plugs can be vexing.
One technique is to inflate the chamber using the small nozzle, then pinch with your thumb and forefinger about an inch behind the plug hole. This will pinch off the air loss until you can get the plug in. In new boats the hole is quite tight, and I put a little saliva on the plug for a little lube (sorry to be gross, but it works).
The other technique is to inflate the chamber, keeping some pressure on the pump, then position your forefinger right next to the nozzle. You can then quickly pull out the nozzle and move your finger to cover the hole opening. Grasp the white plug with your free hand and move it right next to your covering finger and make a quick switch. (Think Indiana Jones in the first movie, when he switches a sand bag for a relic on an altar -- except a big ball won't come rolling after you.)