i've done the one at deer hill (i believe thats what its called) across the road from the cemetary, part of the kintyre way, coming out at the football pitch, really steep quite often slippery route but totally awesome on a bike, by far the best fast decent that i know off in south kintyre, totally KIN-TYRED pushing back up though
What we found was a good afternoon walk - start from the harbour, upto the top of Deer hill by the red route, then pick up the blue route (the longer way round), have a pint(ish) in the glen, then round the green route and down to Port righ, then back to the harbour- that all fills an afternoon.
The best bits where the view from Deer Hill which and the blue route back down the glen, if you followed any of the suggested routes you'd miss one or t'other - so best to mix & match!