I was reading a John Beer article about Gynon a couple of weeks ago, he bought a ticket in advance having called in at Claerwen, drove up to Teifi Pools and went cross country to Gynon from there the following day - it's not that far. I'd have thought a SAE to Claerwen would work.
Never fished it myself but I do fish Teifi pools every year. You have to have some luck on your side with these waters, you'd believe they're empty one day but on others they just switch on and sport can be excellent.
Wet days are best avoided, thanks to the wooly maggots there's no shelter and the force of the rain can be phenomenal. I've never caught a rise to Coch Y Bonddu but that's one of the best time to go.
The trout can grow to a good size up there but even the more frequently caught small fish are a pleasure and beautifully marked