Yea there's a couple of ways to add pressure. I used an electrical tape roll, just the right diameter and stacked some weight on top.
Tip. If the valve has to be oriented in a certain direction, as in, if it is attached to the fabric flap as on the Best kites, before you peel it off, mark on the bladder the direction it sits in. If you're off by 10* or more, it's kinda goofy. I have reglued both valves on the LE and one strut. Holding well for three years. Good to have a spare tube of the stuff in your kit.