Tresiba does have an automatic pusher, but thus far I have had no issues injecting into either fat or muscle. I take 80 units daily and generally inject all at once in the same spot. If I start running out of real estate because of bruises, etc, and decide to use muscle, I split the dose and inject in 2 areas at the same time of day. I don't get the burn I used to get from Lantus either.
Personally I much prefer Tresiba to Lantus. Minimal spike, 35+ hour tail, no stacking, and I can vary the time of my dose if needed (though I rarely do). My basals are much more in control with Tresiba than they ever were with Lantus or NPH.
Even though switching can be scary, I think you might actually like Tresiba ( at least I hope you like it as much as I do). Have a great day!