From Flint I presume he joins the A55 at Caerwys heading down Rhuallt Hill,
You can come off earlier than Abergele at St Asaph Business park to avoid Bodelwyddan and Abergele snarl-ups to get onto the road to Glascoed as the Medz suggests, just carry straight on which will bring you to the caravan site crossroads/petrol station, (Penyrefail on the left) just go straight ahead to Betws -y-r. past Hunters Hamlet,
Have a look on Google earth, you will see the road runs almost parallel to the A55 from St Asaph