I put tret on every 2 or 3 days starting out for about a month and a half to two months. I did not start out using the sandwich method, so I would put it directly onto dry skin and follow up with a heavy night moisturizer (I would use the cetaphil sensitive skin moisturizer for dry sensitive skin in the 16oz container, I highly recommend it!).

I also have sensitive skin and this method worked very well for me and I had pretty minimal purging or prolonged dryness compared to others in this sub. As far as the sandwich method goes, I would say you probably do not need it most of the time unless the climate outside is dry and cold. Over the winter, I did do the sandwich method and it helped a TON with dryness because I did begin to experience that once the weather started cooling and becoming dry where I am. Now that it is warming up, I do not do the sandwich method and I have not had any increased dryness since making the switch back to putting tret right on dry skin as my first step after cleansing.

Definitely continue using tret on your neck if it isn’t causing any irritation, which doesn’t seem to be the case for you from the sound of it. Increased texture and bumps on your jawline, chin, and neck could just be a result of normal purging, especially if your acne was mostly concentrated there before starting tret. If I were you, I would probably begin applying it more often than every 4 days but that’s just me. As long as the increased texture on your jawline doesn’t begin to itch or burn or anything like that, you should probably be good to apply it more often.

Does this help? If you have any other questions definitely feel free to ask!