One way to play yourself is to go back to the old ways of playing board games or tabletop model soldier wargaming. Solitaire play was always something that came up in wargaming magazines etc. Some hex-based cardboard games even had solitaire rules included, I think?.
Make a list of possible ways to do things and then roll a die or pick a card and reference the list. Then do what you told yourself to do.
e.g. make up a list of possible game strategies at the start then roll
1) Hey diddle diddle, straight up the middle. Everyone goes straight forward from where deployed.
2) Attack on his left flank only
3) Attack on his right flank only
4) Pincer - attack on both flanks, refusing the centre
5) Central attack - refuse on both flanks
6) Some other bright idea (e.g. in a meeter - perhaps "advance to the half way line, then let him come to me")
Then before setup (if not a scenario) you roll your die or pick your card and play the game as determined by that. If a scenario, you need to look at how the designer has your force set up initially, as it may restrict your options.
If you want to decide things during the game, maybe make up lists of things a company (say) should do - hold and shoot - cautious advance - all out fast attack etc. Or before playing a particular unit determine a few options in your head and roll a dice to decide which.
Or you could make a set of "tactical cards" with what a company should do and pick one for each per turn. You could if you wanted make up say 50 index cards (from office supply shops) with everything but the kitchen sink included. You could have a stack of cards for "offensive" oriented formations and one for "defensive". Some should be "do nothing" actions - I.e. sit and reserve shots for opfires. A couple of the cards may be marked "shuffle the deck", in which case you reshuffle and pick a fresh one.
A company probably would be the best size of decision unit, other than for skirmish level games.
You may want to roll a die if say the unit has an option to fire at several units - 1,2,3 the nearest MBT, 4,5 nearest non AFV, 6 nearest grunt or ATG perhaps, or simply figure out to yourself in your head the most likely and assign it 1,2,3 and then 4,5 for the next most logical target, and finally 6 for the third.
But figure out a scheme that works for you - and try not to cheat against yourself
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