Further comment

I read a book a while back when I was first exploring this.  The book made the point that the objective of flogging is to increase endorphins so that the experience is actually pleasurable.  In that regard the process is more than just consensual.  It is more of a collaboration.  The advice was to take strokes of various levels.  Have the girl rank them between 1 and 10.  Try to start out at a 3.  Ask her if she wants to go up or down.  She will be able to determine how hard to go. As she adjusts to the experience, she will ask for higher levels.  The girl will learn what turns her on.  I will often work up to a 6 and the girls go into sub space.  It is really remarkable when there is good communication

Another point

I know it doesn't fit the fantasy but another point is to focus on the limited fleshy parts of the body.  That means the buttocks and particularly the "sweet spot" at the lower two thirds location.   The back of the thighs is also good.

Practice makes perfect!

If you have a willing sub, then your winning!  Trial & error.  You will learn what areas are more sensitive, and will leave makes depending upon the pressure you choose.  Every sub is different.  Always discuss limits prior to playtime.

It's all in the wrist....

the more you "twirl" your wrist the more the straps spin together to create more tension and more sting....