The main handles of the Bulgarian bag which are tapered by design are used for gripping during lifting and swinging movements, the user is forced to squeeze hard to hold onto the bag building a tremendous amount of grip strength.
When holding onto the main handles the trick for a strong grip is to effectively use the thumb crease, this is the crease that joins the main handles to the bag and gives you the ideal spot to place the thumb when gripping the main handles.
The straps are used primarily to assist the grip whilst holding onto the main handles, never attempt to swing the bag by the straps. They are used by looping them round the wrists, twisting them around the main handle and then grabbing hold of the handle. They are also colour coded to quickly identify different weight bags whilst training. Remember, if you do decide to use the straps you’ll be reducing the potential grip strength benefits which is a key benefit of Bulgarian bag training.