Only the one reply that's even vaguely attempted to answer the question.?
Contrary to mboy's stab at answering (well done for having the courage to take a guess tho ) a minion is not actually all that great a braking tyre, it does however brake very predictably.
For a tyre to have good braking characteristics the first thing it needs is good braking edges, which a minion doesn't particularly.
A Highroller has better centre braking edges but unfortunately it has weird braking characteristics when braking while cornering or leant over making it want to push outwards.
The Newer Highroller II would offer a far better combination of straightline and cornering braking performance than the old HR or Minion out of the Maxxis DH range.
DO NOT EVER SIT DOWN WHILE BRAKING. the second you sit down you lose proper control of the tyres traction. instead, if you are only able to brake with the rear, shift your weight rearwards and lower as you brake to allow you to get more traction without locking up.. moving your body weight is equally as important as actual brake lever control and power.
I do agree with mboy in that your best bet is to run a very powerful front brake preferably with a short lever throw that can be set-up to bite v. close to the bars. (without knowing more about your particular condition) generally speaking we have more strength in our braking fingers the less stretched out they are at the brakes bite point. this also allows the non-braking fingers to hold onto the grips better while braking giving less hand fatigue.