Your best bet is to go from Kinlochhourn via Barrisdale Bay. First part of the walk is pretty straightforward, mostly along the coast with a few diversions inland and some short, sharp hills. Around 10kms to Barrisdale Bay which is a great place to camp (beware midges though!). I think there’s a bothy there too. From here there’s a great path up over the Mam Barrisdale and down to Inverie. It gets up to about 450m with the option to take in Ladhar Bheinn and Luinne Bhienn. About 15kms for the second leg.
I’m pretty sure you can camp at Inverie…
The alternative route would go from Kinlocharkaig via Glen Dessary but is a much tougher proposition (from memory).