Main path to the little footbridge then there's a trod that takes you all the way to the top, trending diagonally up and across the hillside, up the scree for the last bit.
Go north off the summit blocks then immediately drop left into the gully which is full of big boulders.And secondly the descent off tryfan , looking at going down west gully as never been down it always come down south ridge after a climb or scramble, ian do you mean west gully is 20 yards past summit then drop down it to steps ? I take it you then make a line to the road then ogwen hd and striaght up path on peny ol wen ?
Then a steep path with some long sections of stone steps takes you down the hillside, either carry on down to the road and along that to Idwal Cottage, or cut across directly to the Idwal path... I take a line underneath Bochlwyd Buttress around the 400m contour level, its a bit boggy in places but nothing too bad.