I think all glues are basically the same in terms of their active/main ingredient. But the BRS gel is my go to. You can get similiar, but the small containers are more expensive, so even though the BRS is like $35 I think, you get so much that it's cheaper per fl oz.
Then I use accelerator to cause the glue to harden instantly. After I get what I want, then I go back and put marco cement over it all. Adds extra strength and after 6 months it's hard to find where the pieces are connected. In a few places where I had just a small piece, I didn't do the cement spot, and I can still very clearly tell it's glued. Eventually corals will grow over it, but the "Oh that's not noticeable" when I was doing it is now very noticeable.
In my experience the biggest worry is when you are picking it up and apply force upwards instead of downwards. When you glue it all etc, all the force is down. Some of it is the rock resting on the other rock. So if you aren't careful when picking it up, you can break it that way.
And that happened in mine. On the right side of my tank, the top of the rock originally had a long overhang that went towards the back and curved around a little. It was VERY heavy, too heavy really. When I was putting the rock in the tank, on the way down that piece got caught on my kessil light braces, the 2 little pegs that stick out. It knocked it right off. So now that is just in the middle, home for a diamond goby. Couldn't deal with the upward force.
Some of my hangs are much larger than they appear. On the left side, it looks like the arm starts on the sand, but that entire piece is actually an overhang. And then it goes towards the right about 2 feet. Believe it or not, it held no problem just like that on my kitchen table for days. But it scared the crap out of me, so I added a tiny little column half way down. On the right side, in the pic it looks like maybe an 8 inch or so overhang. It's actually a big long arc that curves from back to front. It starts on the high point in the back and comes forward all the way in front of the base rock while curving left.
All done with superglue and cement. Still a little hard to tell in this image, but you can somewhat see it in this picture by looking at the shadows on the sand. On the left side of the rock, that's just a big ledge sticking out. These pics are from about 8 months ago. You can see the cement in these, but they don't really show up at all now.
down at the bottom, the little piece that sticks out on the left side is also a ledge, but you can't tell because the sand comes up to it.
Another view of the same rock, more on the left side. There are lots of smaller little ledges that stick out all over. Most of them have coral on them now.
It's all just 1 big rock.