Maybe try using this stuff? It is probably premixed in your fluid already but maybe it needs more. Seems like it is designed for issues like yours.
https://www.amazon.com/ACDelco-10-4003-Limited-Lubricant-Additive/dp/B000QGMXSU
Bought a new 1LE Camaro with the man's trans. Shifts smoothly once warm, but it takes about 15 minutes to reach that point. I'd like to improve upon the cold shifting performance. Factory fluid is the #88861800 aka rebadged Dexron III.
Looking at full-synthetic alternatives I've found Motul...