Reefing at the goose neck is the simplest system and involves less friction than other methods. Do you have a winch at the mast?
You should have leech reefing lines that run the length of your boom and exit at the boom end. A mast mounted winch can be used to harden the leech reefing lines. The two u-shaped fitting are ram's horns to which you attach your tack when reefing.
Any cunningham controls would likely be attached to the mast tabernacle. It is usually a system of blocks with a hook for the cunningham cringle.
Pictures here http://www.zsparsuk.com/slaboom.htm