If you've pretty much mastered your leg break and you're now fishing around for a variation the flipper might be an option for you. In his book the The Bowlers Art, Brian Wilkins makes a good case for having the Flipper as one of your variations. Once you've developed the muscles and learned the basic technique, there is scope to change the position of the hand to create variations within the variation as such.
So, if you're in the UK and you're thinking ahead to the next season and developing a variation, you can get started with the Flipper without having actually bowl...
One of the issues that stops people in their tracks when they start to work with the flipper, is the fact that they don't have the muscles developed in the hand, fingers and thumb to impart the spin.
My suggestion therefore is, over the winter you get yourself a smaller lighter ball - you could start with a tennis ball and start flicking the ball out of your flingers in the manner required. The technique is to grip the ball as indicated above. You can grip with either one finger, two or three over the top of the ball - whatever feels good for you. Most people find that the power to impart the spin comes off of the middle finger. If you're confused to how you actually perform the action - it is the exact same physical action as clicking your fingers to a music beat - except that there's a ball between the finger and thumb!
Do this all the time - start with a small ball - maybe even a table tennis ball? Do it with apples, oranges - anything as long as you're able to give it a good click! You might find that initially you have no control over where it goes, but in time, it eventually starts to come out of the hand in the direction that you want it to. At this stage start to visualise and practice the release and arm position, thinking about how you'll bowl it.
Do this over the winter consistently and that part of the action will be in place, all you'll need to do in winter nets is tie the release action to your bowling action. It should be relatively pain free.
* I wouldn't take any notice of any of the stories you read about people taking 5 years to develop their flippers, I went from trying it for the first time to pretty much having the basics nailed in about a week (That was a week off from work - a few hours a day).
The image here is the version I describe as being the bog standard Flipper, this goes down with a vertical seam with back-spin. On hitting the wicket it might do one of several things. If you can hold your nerve and bowl it slowly, it can stall massively with the back-spin That method used as a variation amongst Top-Spinners or over-spun Leg-Breaks can be very effective.