I found the best solution is a knot system I made up I call the Kansas City Hitch. One of the problems I found is when your raft is 20 feet from the tree or bush, but you have a 75 foot bow line. It can be a pain to run all of the extra rope around a bush and tie a knot with all of the excess line, so I just feed a loop around the tie down anchor, keeping the line from the boat and the excess line on the same side. Then I clip a biner to the loop, tie a bowline with both lines (from the boat and the excess) and clip the biner to the double bowline. The double bowline is easy to untie to readjust, but you could also tie a bowline in the loop around the anchor and clip it to a prussic on the boat line. Lots of variations can be made.