you don't want to ever cut down body fat quick if you want to preserve muscle.
the best thing to do is not gain fat to begin with, but if you do get lazy with your diet and exercise and need to drop fat you do it slowly. muscle will burn away just as fast as fat will
tabatta/HIIT/CF style workouts shed fat. Used appropriatly in conjunction with strenth work its easy to make muscle gains and cut fat BUT they do burn a lot of cals so you may find you actually have to eat more or you will quickly overtrain.
This is what I did and have lost weight and body fat.
Low dose of test.. to start with
But a big focus on my diet. Alot of tuna, protein shakes etc.
I've cut out sugars (food and drinks) and have focused on putting protein in my body.
1 gram of protein for every pound you weigh.
I'm sick of tuna- but it's magic man..
Also watch what kind of protein drinks you take. Alot of them are loaded with sugars.
Beverly International puts out a good protein shake without the sugars.