I've Got The Modeling Shakes......

 When I bear down and really concentrate on a hard to fit part or a really intracit paint job I get shaky right at the most critical time. I suffer from task specific Focal Dystonia in my right hand. It sucks. Perhaps you have a touch of that. Stress makes it much worse. I had to quit playing golf and get by in tennis with a rediculously extreme western grip. I actually have an appointment to go see someone in the next couple weeks. It only took me 25 years this is the first time I'm actually going to do something about it. I read that Parkinson medications or even Botox is a treatment. We'll see. Google  focal dystonia. Get a second opinion for sure.

I'm 53 as well and I find the same thing.  Doctor says my problem is mostly the Albuterol I have to use for my COPD.  Besides resting my hands as described above,  I have found that using a breathing technique I was taught in therapy called "pursed lip breathing."  This is basically inhaling calmly through the nose, then exhaling through the mouth with your lips tightly pursed as if whistling, so you can actually feel some back pressure in your chest.  Try to take at least twice as long to exhale as it took to inhale, but the longer the better.  I use this to control shortness of breath, and seems to help calm my shaky fingers down before I start painting, etc..  Might be worth a try, anyway.

Yes to about everything said above.

Plus I'd like to add that I fine mine starts when I've been "working" perhaps a bit too long and almost too focused. And, as you say, it's always something small and finicky.

My 2 cents is to walk away for a bit, get away from the bench.

It is nice to know I'm not the only one.

stikpusher

Also deep slow breathing can reduce the shaking as well.

Extend this process to all things. Master your breath and you master your mind,the body will follow.

It made sense to me

We all shoot, right?

To me, it's the same. At least when I have my M14 out at 100 yards or the 7mm bolt rifle.

Look, relax, exhale, fire. Old friend of mine, Gunny; taught me to remember the shot. One max every minute. Sit there and think about it.

I find that I control the shakes best when I know what I want to do ahead of time.

I model incredibly slowly, but I trust my action ahead of time.

I know that makes no sense.

I am something of a coffee fiend at times, and when I have more than I should before a bench session, the shakes show up. I counter them by placing my hand against the work bench or some other non moving surface to steady my control.

Also deep slow breathing can reduce the shaking as well. 

I'm right handed so obviosly that's the "painting hand"

What I do is extend my pinky and rest it on the workbench. It helps.

I'm also a  smoker (I know... I know.... I have been cutting back lately. I'm down to 6 or 7 a day.  Unless I'm in a bar...... then I smoke a pack in an hour...... and come home with my  vocal cord's feeling like hamburger!) So sometimes when I'm about to paint i smoke to lessen the hand tremmer's.

I DO NOT RECOMMEND  A N Y B O D Y  STARTING SMOKING JUST TO EASE HAND TREMBLING !!!!!    ( or for any other reason !!! )

Trembling DOES come in handy for wethering ( just load up the brush with Rust and "twitch" away!