I decided to put the brackets on while the vehicle sits on level ground, I already have about 5" of lift so its pretty easy for me to get under it, but I think even on a Jeep with less lift you should be able to work on it on level ground, though with the drill you may find it easier to do this part on ramps.
If you wheel your rig your crossmember is probably pretty messed up, so you will need to bend certain parts back into position, like on the corners I folded the lip over my bolts so I couldnt get them off, a big screw driver worked well, much better than a BFH.
Once you've done that place a jack under the crossmember and losen bolts on both sides.
now on the side your working on, take the bolts out completely and lower the cross member enough to get the bracket on. Slide the bracket in place, then tighten the crosmember bolts again.
Drill your holes. Now remove all the bolts again and take the bracket back out:
Clean out the holes of any shards and what not, paint over the exposed metal from drilling.
Spray on ruberized undercoating:
Now remount the bracket, and tighten the bolts on the crossmember so it sits flushand in place.
After this comes the fun part of fishing the nut plates into the frame rail, my only advice is to be patient, to fish them in put them in upside down then ones in the hole, poke it so it flips right side up. If you have skinny fingers you should be able to push it in place, if not you will need bailing wire.
Once you have the nuts plates in place tighten the bolts (don't forget to put thread locker on), you may have to redrill out some of the holes to get the bolt to thread as I had to do.
Now do this same thing on the opposite side. When both sides are on, torque the front 4 bolts (bolts that go to nut plates) to 85ft lbs and the crossmember bolts to 30-34 ft lbs.
Brackets are on