I have done it on my Lexus it should be very similar.
1. suck out brake fluid from brake fluid resevior (use a baby feeding tube);
2. pour fresh fluid (make sure it's right DOT#, use sythetic when possible) into brake fluid resevior, note that fresh brake fluid is lighter!
3. Now jack up rear passenger side, take off wheel, find the bleed nipple, turn to open the nipple. I put a plastic tube on the nipple that lead to a drain bottle;
4. Get into the car and on a Toyota you may have to start the car. Make sure you have parking brake engaged!
5. Pump brake many times. You'll see stale fluid and air bubble coming out. Check brake fluid resevior and add fresh fluid along the way;
6. Check rear passenger side nipple. When you see fresh fluid coming out (lighter color!) turn to tighten the nipple. Turn car off! Make sure NO AIR BUBBLE coming out as this is your problem with sagging brake peddle. Put wheel back on. Lower the jack. You are done with this wheel.
7. Now proceed to the next wheel. Remember you want to start from the wheel farthest from the engine and move to the closest. Everything else is exactly the same.
8. After finishing all wheels, check fluid level. Put things back and test drive. REMEMBER PUMP BRAKE SEVERAL TIMES BEFORE start driving! Make sure brakes are firm before driving. Reason is after bleeding/flushing the system is not pressurized and so that brakes are not engaged, this may cause accidents!
9. Check your reseviour one more time to make sure brake fluid level is correct.