1. Take cold showers. The whole shower doesn't have to be cold, just at least half a minute or so.
2. Build cardio-vascular endurance. At least 30 minutes a day. Try running/jogging, walking (or a mix of the prior two if your not in good shape- i.e. run or jog for a minute, walk for five, and so on), or tai chi or whatever.

By doing these two things, you lessen sensitivity and decrease negative stress, which are the causes of your blushing problem.