As an afterthought, the route we took had a couple of wee points at which you might conceivably pause & scratch your head wondering where to go, so it can't hurt if I give a bit of detail.
Firstly, although parking always seems to be at a premium near Coileitir, there are actually a few car-sized nooks and crannies if you drive onwards past the gate on the left leading down to the house (now rather nicely refurbished, incidentally). There's no need to panic and block the first passing place you come to. You can leave that to the canoeists and fishermen further up the road.
Through the aforementioned gate, down the track, over a bridge and then curve to the right where you'll see the house, and a wee sign diverting walkers round the garden. This is very boggy, but it disny last long. Once back on the main path you'll notice an obvious track leading off to the left. Despite the fact that there's another sign there, pointing walkers along the main path, in the direction of the next bridge, we spied a couple of folk who'd wandered up the left hand path and then had to backtrack quite considerably. I think that path runs up the east side of Glas Bheinn Chaol (the biggish hill that splits the two burns, the Allt nam Meirleach and the Allt Mheuran) and is quite possibly the normal descent route from Glas Bheinn Mhor.
The route we took was the same one you take to Ben Starav. The path is obvious, a bit wet, but passes some marvellous wee waterfalls and potential swimming holes - temperature dependent of course - as it gains height. We walked past the point where you would swing right to start the slog up the north east ridge of Ben Starav, and continued up the west side of the Allt nam Meirleach.
The path is unmistakeable in good weather. It gets pretty close to rather sizeable drops into the burn on your left, so if you're as paranoid about your dug as I am, you maybe want to practice the whole walking to heel thing at certain points. The only bit I think could realistically cause a problem though is at the head of the burn, because there really is just a sudden gorge, or ravine or whatever, which although deep is also very narrow. It's obvious enough on the way up, because you're following the water course, but on the way down, if the visibility was poor, it genuinely seems to appear out of nowhere. And just at a point where the path is very close to its edge.
There are some nice flat slabby bits not far beyond it which make an ideal spot for a sit doon and a sandwich before the last steep pull up to the "766m col" as the books and the map seem to describe it. Again the way up here is clear enough, although the path is a lot less distinct than before. You're looking for the easiest way up though, so you can't go too far wrong. The views open out as soon as you reach the col. Cruachan is an awfy pointy big bugger!
Beinn nan Aighenan didn't look as far away in the sunshine as it did in the snow the last time I was there, but it's not terribly clear from the col what the way up it might be. In the event, there's another reasonable path down to the bealach, and a fairly visible track up the north east nose of the hill. I wouldn't bank on being able to follow it with much confidence in the winter, to be honest, but again there are various options to pick your way round the rocks. It never gets uncomfortably steep or craggy, even for labradoodles.
The wee pools that appear every now and again were doing a lot to keep Molly (a) cool and (b) interested. Unfortunately, being well above the treeline, there were no sticks lying about that you could throw in for her, so she just had to stand shoulder deep in the water, looking hopeful. And refreshed.
The section from the bealach to the top of the hill isn't actually that bad. It looks worse from the col than it is.
All we did was retrace our steps thereafter, but of course from that col Glas Bhenn Mhor isn't all that far away, if you're anxious for more mountain action. We were swithering about it, but we had spent too long fannying around at rest stops, soaking up the sun and taking in the views with the result that a six hour walk had taken us nearer seven and a half! Still - why rush it when you're having a right good day out, eh?