It would be best if you have a friend that has done this before to help you, you need a second person anyway. You will need the procedures for the antilock system, on some, you just remove the plug and bleed them the normal way.
In the future, with antilock brakes, you should always open the bleed valve when compressing the piston back into the caliper. I don’t see anything wrong with using a c-clamp, I use a large pair of channel lock pliers myself. It looks like you didn’t do any damage this time, but the antilock brakes do not like large amounts of reverse flow in the system.
After any brake job, you should flush the system. It is preferable that you don’t get any air into the system while doing this. even though it is best done with two people, I recommend that you get a one man bleed kit. They only run about $5.
You will need to put all four corners of the van on jackstands and remove the wheels.
Use a bulb, like a Turkey baster to remove most of the brake fluid in the reservoir. The fill with fresh brake fluid. Start at the passenger side rear wheel. First put a box end wrench on the bleed screw, then slip the hose of the one man bleed kit over the nipple of the bleed screw. Hang the bottle above the bleed screw.
Now timing is critical so make sure that you and your helper have a good communication system worked out, and I don’t mean walkie talkies. I mean that the one at the brake gives the command and the one in the drivers seat responds when each command it completed.
Lets call the two positions brakeman and driver.
Brakeman calls "press"
Driver steps on the brake pedal and responds pressure
Brakeman opens bleed screw, driver responds “down” when the pedal goes to the floor
Brakeman closes bleed valve and calls "up"
Driver lifts foot off brake pedal and responds “up” when the brake pedal has returned to its up position.
Repeat until brake fluid starts coming out clean.
Repeat for each wheel, rears first, then fronts.
Every time the bleed kit’s cup gets full, call “hold”. empty the cup, check and add brake fluid to the MC reservoir.