Personally do not have much experience with using raw honey on the scalp. For me it just seemed too messy.
However, in the study they simply applied the honey-water solution to the scalp at the same time as all other affected skin and left it for 3 hours before washing. No mention of any special recommendation for shampooing were made.
Another person recently shared her approach in this comment.
The ACV vinegar treatment has been described in more detail in the “Treating Seborrheic Dermatitis With Apple Cider Vinegar” post.
For additional information please check the comments section of that post. Lot’s of good information there.
Hope that helps. All the best.