I would like to join in this topic (as my first comment) I recommend any (new) midi USB mixer that are sold under the 100s - since they save a tremendous time in your workflow. I am using the
midi2lr currently with ver. 2.2. It is awesome. Since I am from the begining there I can't tell you much for the learning curve. IMHO for the basics pretty simple, advanced GUI functions (configuration-wise) would take some time.
I am no affiliate there, but more like an evangelist. An (expensive) alternative would be
Loupedeck. Along the price a second setback would be its limitations of buttons and sliders.
On the other hand as Victoria says - best would be motorized, but not the cheapest option one like the
BCF2000, which is the best for the moment as button & slider quantity / price.
I personally use (both in the same time) the
AKAI MIDIMIX & the
KORG Nanokontrol 2. Before version 2.2 there was a problem with knob delay - now they have fixed it. I use the AKAI is for major general advanced (and well hidden in GUI settings such as shadow/mid/high light splits, regular high, mid, dark tones... etc. The Nanokontrol I use mainly for local adjustment settings on the fly. I do have custom personal templates ( like for skin, eyes others but as long as they are not obtainable just as right-click I feel it to be faster like that. And every picture has small refinements after all
Additionally the motorized feedback e.g. setting on 50 knob on 0 was easily solved by full slide both sides untill the hardware setting passes through the software setting. As easy as that.
The truebeauty for anyone reading this topic is that one can experiment in the nick of the time by using the true power of Lightroom.