I have done GRC's. I was going to do Flagstaff tonight in fact but I just completed SERE Performance's 40 hour challenge in Tucson last weekend and i didn't recover fast enough. Still can't feel my left toes. Pack was over 60 lbs for that. I am doing 3 more gorucks in the couple months.

You don't neccesarily need to train with the bricks and certainly do work up to it. Start with 2, then 4, then 6. You can find videos how best to wrap them.

key is to get them high in the ruck. Don't want them near your lower back. The GR1 ruck is my absolute favorite ruck. Life time warranty. Its not perfect but bombproof. I use it for my EDC pack. If you don't have a pack already, I know a lot of guys who use the Marine ILBE, Osprey's and Mystery Ranch. I love MR packs. As spendy as a GR1. Cheaper and the exact same pack as the most popular MR pack is the Camelbak Trizip that came out last fall. They worked with MR on it. Super comfy. Loads well. Don't go cheap on a pack for 6 bricks. I shredded, nay, destroyed a 5.11 pack in 10 minutes fully loaded. The shoulder straps frayed right at the top connection.

Any other questions, ask away.