I got my Behmor just over 15 months ago and have done over 100 roasts on it now. I spent the first few months of last year getting to know the machine and it's basic operation. I also did a lot of reading online to gather ideas on how to use it best.
About this time last year I started experimenting with the main variables of manual control, preheating, batch size and cooling method. What I found is that the thing that makes the biggest difference to the quality of the roast is getting the correct batch size and using the correct batch size and profile settings.
Most of my successful roasts for quite some time were 250g batches using the 200g setting with either P1, P2 or P3 auto settings depending on what coffee I was roasting. I experimented lots with manual control and found that you actually have more chance of success by choosing the right auto setting than by going crazy with manual control. Most of my roasts these days are on auto until close to 1C. I always at least lower the heat at 1C, but sometimes I increase it for a minute or so before 1C too if required. I always increase drum speed when I go into manual mode too, just for a minute or two.
I found that preheating and cooling method make a difference as well. Because the Behmor is so small with not much thermal mass it's greatly affected by ambient temperature. Living in a relatively cool climate that can experience fairly large temperature variation I found that preheating added some consistency, and I was able to confirm this through profiling my roasts using a Heatsnob. So if you're ambient temp is consistent enough without preheating it's probably not necessary. I tried all the different methods and settled on preheating with tray and drum out with the beans loaded in the drum ready to go. I preheat to a set temp (usually between 80-100deg 'B' temp) then load as fast as I can.
Cooling is kind of the same in that what ever you do it's about being consistent. I found that cooling in the machine was difficult as I was struggling to work out when to stop the roast to allow for a bit more roasting to occur due to the amount of heat still in the machine. So now I cool externally in a sieve and fan setup that I've put together. Again I'm aiming for consistency and what works for me won't necessarily work in other situations.
Hope this very long winded explanation helps a little.