Ive been there a few times.
The farmer up there actually doesnt mind if you go up to it, just knock his door and let him know and he will open the gate for you, He usually keeps sheep or cows in the field so expect loads of mud and cow pats and sheep crap. Go along the piggery brae road and go up the path directly into the farm.
The castle itself,you can only get into the barreled room area which i understand was the kitchen. The upper areas are innacessable unless your an amazing climber. Theres the remains of a lovely wee staircase in it.
There was a book translated from old scots into english by the owner Poet William Hamilton (1665-1751) Blind Harrys "Wallace" which inspired the book Braveheart, then turned into the movie. Rabbie Burns was also a big fan of the book. He stayed at the castle regulary.
Heres a shareware book that is avaialble.
http://www.sharewareebooks.com/eBooks/E ... /inbrowserI hope you enjoy your visit.
Dicky.