Learning to idle.
What is the weight distribution? All on the lower leg, on the seat, or some combination of both? Hard to tell from videos. Just wondering.
I’m still learning but I like both legs involved. Maybe 80%-20% or 90%-10%.
You should be sitting in the seat as much as you can. Pressure on the pedal is just enough to make them do the job. I use metal pinned pedals for more traction.
Pressure on the seat and pedal that is down then lightly use your foot that is on the other pedal to rock yourself back and forth. 
A LOT of pressure on the seat, or mostly on the low pedal?
I am barely touching the seat, just enough to know it’s there. I seem to want to stand up on that low pedal, I guess I need to concentrate on not doing that.
Yeah, a considerable amount on the seat - just like when you are riding, you’ll find that if you get into that habit of sitting when idling you’ll exert much less energy.
It’s ‘bad form’ but I idle like you said, I pretty much stand up with my weight on the low pedal.
When you are simply travelling on good even surfaces, try and ride a very evenl cadence with almost no fore and aft pressure on the pedals. That will drill you into the necessaries to idle with minimal input from the feet.
And while you are going along like that, you can occassionally try and slow right down.
It also enahnces your ability to travel in malls full of peds where you have to do a lot of VERY slow speed until you get a gap you can slip thru.
(I am still having trouble though when I am on the giraffe, espoecially if I really slow down or want to reverse - that’s when I have to press with a lot of weight on the pedal, as soon as I get a little out of whack.)