I went up Tryfan and Glyder Fach together, really nice walk. About 7 - 7 1/2 hours shoudl do it taking it easy.
route being
park car park by Lake Ogwen at the foot of Tryfan. Go up
Go down the other side.
(If you didn't fancy Tryfan going round the Cwm Tryfan side looks an easy option, the ascent from this side - see below - was pretty gentle onto Glyder Fach.)
Bwlch Tryfan to the miner's track,
turn right, Then up the ridge, just keep going, easy ascent.
Down via Y gribin to lyn bochlwyd. Fun but maybe not in slippery conditions. Not so bad though. Plenty of mountain goats to keep you company anyway!
Glyder Fach is amazing on top. Out of this world rocks!