When you squeeze as if you're terminating a flow of urine it's the PB muscle you're using and that's also what guys feel when it contracts. Over time you can build it's strength and endurance just like any other muscle.
Your goal obviously is to build enough strength and control with the PB muscle that you can contract it very forcefully for several seconds at a time. That may not sound like much, but believe me it does take some practice.
One way to do the exercises is to start with sets of 5 seconds in duration squeezing as hard as you can. Rest 5 seconds, then repeat. Do five sets like that in a row. You'll get 25 seconds total of contraction, but with rests built in throughout. Do this twice a day, everyday for a 2 weeks. Third week, 10 seconds contraction everytime, but still only 5 seconds rest between them.
Ultimately you want to get to where you can contract the PB really efficently and forcefully with only 2-3 seconds rest every 15-20 seconds. Dont be discouraged though, it really doesnt take that long to be able to do that.