Afan - FANTASTIC place to ride...
Are you only there for the day?
Get there early - do whites level first IMO, followed by the wall...
Either that, or do the wall first, off to the cafe for lunch, and then "july" second (this is the climb for teh start of whites / skyline - you then follow the signs for skyline, and take the first marked shortcut = this will be obvious - you get to a sharp left on the trail, with trail signs left and right. The left will take you up a stepish rocky trail, and on to the rest of skyline. Go right- its down hill, and fairly rocky. At the bottom of here, I think you turn right and you then basically do the last 8k or so of skyline. The last climb on skyline / july isn't nice, but the last descent is AWESOME (unless you've been to the alps - then it is still great, just over too quickly.)
IMO, do NOT do the full skyline - out the back it is full of fire roads, and fairly boring, and fire-road based.
Stick to the Wall / whites / july, and you'll LOVE it!
HTH.