Isometric exercises are compatible with the B Strong system. Essentially, you will want to substitute a 3 second isometric contraction for each repetition of an exercise movement. Once you have the belts inflated, and instead of doing the usual exercises, perform 3 sets of 30 isometric contractions of the interested muscle.
When contracting, hold the contraction for 3 seconds and then relax for 1 second and repeat 29 times before resting for 30-60 seconds. Perform 3 sets of these 30, 3 second isometric contractions for a given muscle group before moving to the next exercise. These isometric contractions are particularly useful if you have a joint injury that is aggravated and painful if moved during exercise.
You can combine isometric exercises with movement exercises in other areas of the body. One thing many find that are interested in big hypertrophic muscle gains is that isometric contractions and very slow moving contractions are particularly effective in building muscle. One can also combine isometric and normal contractions in a given exercise. For example, when doing 5 lbs arm curls, one can hold an isometric contraction at the end of the range of motion, both with the arm fully flexed and the arm fully extended.