Per my owner's manual, I always start my engine at low idle speed ~500rpm. After oil pressure is established - a few seconds at most - I use the idle speed control rocker switch to raise the idle in 25rpm increments to ~700rpm. Then I use the smart wheel cruise control to hit 1,000 rpm to build air pressure and warm the engine as quickly as possible. My Allison manual recommends 700 rpm input shaft speed, so once I've established that as my base idle, it remains there. On shut down I use the rocker to reduce to low idle again for the next start up.
I'm not making this stuff up, I read the manuals.
