Short version: use the QB editor to create a force as large as you want (just go over budget the game will not let you start but you can still purchase) then record what you bought (including soft factors) and recreate that force in a scenario using the map of your choosing. Play and have fun...
I had a much slower computer back then so yeah it did take a long time to load. Like go make a coffee and a snack long. I am not a huge micro manager so orders while longer than for a small battle for sure I really only had a large amount of work to do for a smaller number of units on the pointy end.
Even for smaller battle I often manage the turn by thinking of the battle as a series of smaller battles. That lets me keep the number of units I have to think about at once to a manageable level.