The trail begins at the Ben A'an car park; it's owned by the Forestry Commision and costs £3 per day to park (coins only, no card reader). It's not a huge car park, so if you're planning to tackle Ben A'an on a weekend, I would get there early. We went on a weekday and arrived about 1 pm and it was almost full then.
Though the trail isn't signposted (we saw a small sign a couple of hundred metres into the trail), it's easy to follow; you would struggle to get lost to be honest. Put it this way, if I have no problem following the trail, you'll be absolutely fine.
Within a few hundred metres, you're rewarded with stunning views over Loch Achray and the surrounding area. The trail starts off quite steep and remains pretty steep for the majority of the hike. There are a couple of flat-ish bits, but for the most part, you're giving your calves and knees a good workout on the way up.
After about 20 - 30 minutes, you'll come across a bit of a crossroads but keep going straight ahead. It's pretty obvious that you don't need to turn off, because if you look left you'll see the path has quite a big gate. Not 100% sure what it is, but it kinda looks like forestry access.
As you get closer to the top, it looks like the summit is a huge lump of rock and you might wonder how you're supposed to get to the peak. Fear not. The rocky path leads you around the back and to some absolutely stunning views over Loch Katrine, Loch Achray and the Trossachs.
We sat down on a rock, overlooking Loch Katrine, feeling a slight breeze on our faces and questioned whether or not the view was even real. Obviously, we knew it was; it seemed so vast and on such a beautiful day it was hard to believe it was real. It definitely made the steep slog worth it.
To be honest, had we researched the walk a bit more and realised how steep Ben A'an is, we probably wouldn't have done it. I'm not going to lie to you, we aren't super fit. We get out quite a bit, but the majority of our hikes are pretty easy. I guess this is a lesson in forcing yourself to do things you think you can't do and pushing yourself.