The following are two great sphincter exercises, in order of
effectiveness, IMO, which worked for me - it took me 18 mos. from RRP
to get continent (only slight leaking even standing/walking), where
normal Kegels were a dismal failure - I'm certain that if I did the
following instead of Kegels I would have regained continence a lot
sooner; Kegels just didn't work for me:

1) There are two parts to this first exercise. THE FIRST PART: in the
evening when you are relaxing after a long day, and sitting or lying
around, drink 3 or 4,  8 oz. glasses of any liquid during a period of
fifteen minutes or so. I like to drink soy milk, but regular milk, like
chocolate milk, would do; juices would be fine too. Better to do this
when your bladder is already near your current bladder capacity (i.e.,
you haven't pee'd in awhile). After drinking the 24-32 oz., don't get
up until you can't stand the pressure anymore and you absolutely have
to go. You should be able to hold out for at least an hour before
getting up and going to the bathroom, but this depends on your current
state of progress. B4 you pee you'll feel the pressure from the
increase in bladder size, and your sphincters natually clamping down
harder to hold back the flow. Then go pee when you can't take it
anymore. THE SECOND PART: in the morning, when you get up, don't just
run to the bathroom without thinking. First, sit on the edge of the bed
and concentrate on how the muscle contractions feel naturally holding
back the urine flow. Then gently stand up and try to maintain the same
feeling (i.e., try not to cause a change in the natural muscle
contraction). Stay standing for a minute or so and concentrate on, and
feel, the natural pressure/muscle contraction. Then walk to the
bathroom trying to maintain the same pressure/muscle contraction. You
can add to the natural contraction a little, but don't do anything
major. As a result of doing this exercise even once you may notice a
big improvement within a day or so. What you have just done is increase
the strength of the specific/exact muscles you need to get stronger
(they got stronger overnight after the first part of the exercise) and,
with the second part, you have trained them to contract naturally, and
thus work effectively, when you are standing up and walking. I would do
this exercise up to 2 or 3 times a week perhaps, but you can benefit
from it if you only did it a couple times a month.

2) When you are sitting and lying around, at a time when you can
concentrate, and aren't generally exposed to distractions, and
particularly when you haven't peed in awhile, apply a very gentle and
slight contraction of the sphincter muscle, and hold it this way for as
long as you can concentrate on it. I say "very gentle" and "slight"
because if you overdo it you will wear out the muscle and regress
instead of make progress. It's good to do this after you feel the
muscles naturally contracting a bit because then you will know the
exact muscles to apply pressure to. I think this type of exercise is
better than Kegels because it is closer to what you want the muscles to
do (stay steady) and you are getting closer to the exact muscles that
need to get stronger. IMO, Kegels are generally too vague in terms of
the particular muscles applied and strengthened to be of any value, and
can often interfere with the strengthening of the precise/specific
muscles needed for sphincter control. I know this is similar to the
start and stop while you are peeing routine, but I didn't find that to
help for some reason.