Julez I finished 25 rad sessions last Wed.
Put the strata, or whatever you choose to use, up to collar bone to under your arm pit. After about 10 sessions for me I could tell where the rad was treating so just put there.
My routine since day 1 of rad:
Strata first thing in am
Strata immediately after rad ie in change room
Strata before bed.
Shower gel: only used and still do the QV wash.
At times I felt a bit dry so used some QV in between Strata.
Post rad:
Same as above but I needed to apply once or twice during the night as I developed a small burn area under arm near lymph node scar which was quite sore and uncomfortable for 3 days. This started about 3 days after finishing rad.I am now 7 days post finishing and can tell my skin is healing.
I did get a bit pink and tender, especially by the end of the week.
I am on to my second 50g tube of Strata. If I need more I'll just use QV or similar.
I hope this helps.