i think it's funny how people seem to think that resisting restraint will only get you more hurt. sure, when someone has a needle and some pepper spray you shouldnt resist, but then again very few programs still imploy thorazine and pepper spray, thats reserved for mental institutions and actual prisons. now getting away from a belt loop restraint is fairly easy, i did it when i was escorted. while they were escorting me down the stairs i threw both escorts down, jumped over the railing one flight and ran downstairs. the only thing is my mother warned them about this, and they had a big guy waiting for me downstairs who i thought twice about resisting against. bassicaly what i did was they belt looped me. i was a stair below them, so i hooked my right arm under the escorts left, and flipped it around so that my right arm was pushing into his shoulder, and my left hand was holding his hand in a contorted position. basic kinda arm lock. i could have broken his arm, but instead i kicked him down the stairs. all this took a fraction of a second. the second escort was on top of me instantly with a bear hug, all i had to do was give him a nice hammer in the balls and he was easily thrown down too.
yes, brazillian ju-jitsu is very excellent for this purpose. also look into Akido and Systema, which is what i study. stay away from any martial art that involves alot of forms (sets of moves), and relies on strikes e.g tai kwon do, kung fu, karate, boxing, all that bullshit. those only breed bad habbits which get people very hurt in real-life situations. akido and systema is good because it teaches instinctive reaction and reversal of energy, rather than just how to punch and kick, which they both have very little of.
oddly enough you would think that after that they would just handcuff me and treat me like shit till they dropped me off. but no, they were actually very respectfull after that. not neccesarily intimidated, but they knew that i was out of their control, and that the only way to make me obey was through positive reinforcement. it was pretty funny though...it was almost like they were sucking up to me.