This can be a sensitive subject with so many different variables that... it will numb you and your horses minds.
I did A LOT of research. Most of it garbage for me and my horses. I stopped... and looked at the what, when, where and came up with the whys.
Once I figured those out I revised my whole thinking and understood the problem that I had... and my horses.
New plan and I can load a horse in 30 seconds without any duress or harm to horse OR me. IMO... after 4 minutes... you got big trouble. You've been fighting your horse and reinforcing the horse NOT wanting to load.
30 second load. The faster is safer and it's done.