Very true, John.
Forearm strikes can take various impact directions, including effective 'spearing' with both radius and ulna can serve as 'entries' pre-empting an attack,mostly directed at the neck and 'triple warmer' points.
Yes, both Bob Rosati and Joe Graziano are superbly conditioned.
As we condition,the mental image should be, as you say, your arms and shins as natural weapons...sticks_ axe handles_
And as you point out, the daily self/conditioning is the key, in addition to what we do with a partner in the dojo.
Years back I used to use rope wrapped clubs, but for the last 25 years or so, I have been using the 'iron arm'
The routine for me is a simple one that allows for no missed sessions:
as I keep all my shoes at the bottom of my basement stairs in racks along the wall_I am forced to go down the basement at least twice a day for shoes on and off.
To the right of the stairs I placed a long table where I keep my gi bag and my gym bag.
Next to the bags I have two of the 'iron arm' sticks_ which by force of habit I use to tap shins and forearms at least 30 times each, followed by vigorous 'rolling' over the tapped areas with a rolling pin_ if you can find a grooved one...even better.
This way, you train yourself to tap at least two sessions a day.