Now you know where you are going at Aston Hill I’d say head back up there again on your own and spend the whole session on the red run, riding it over and over until you are more confident, focus on getting just one section right at a time.
I’ve only just started riding downhill myself, Rogate is local to me, the first time I went I hated it, felt just too hard, but I forced myself to complete 10 runs down one track in that first afternoon. There were sections I couldn’t ride (still on this one track), but I just built up to them over the following weeks.
Tuition definately helps. I had a session with jedi about 18 months ago, well before I thought about DH. Everything he taught me can be applied to DH.