Agree with the comments so far that emphasise cutting off their resources early game to prevent teching up.
This is relatively easy to do if you play Brits (if a little unsporting, perhaps) by putting a few trenches down at key choke points and consolidating all your resources behind these lines (move your HQ up fairly quickly and don't worry about temporarily leaving resources unsecured behind you).
If you do find Stukkas are bombarding you from deep behind their lines mid game and you have gone Commando, watch for where they are firing from (icon shows up on the mini-map as their rockets fall) and drop a tetrarch tank behind it to take it out. You might lose it if there’s a load of AT around but the tetrarch is manoeuvrable enough to be able to inflict a bit of damage before it's toasted.
This is relatively easy to do if you play Brits (if a little unsporting, perhaps) by putting a few trenches down at key choke points and consolidating all your resources behind these lines (move your HQ up fairly quickly and don't worry about temporarily leaving resources unsecured behind you).
If you do find Stukkas are bombarding you from deep behind their lines mid game and you have gone Commando, watch for where they are firing from (icon shows up on the mini-map as their rockets fall) and drop a tetrarch tank behind it to take it out. You might lose it if there’s a load of AT around but the tetrarch is manoeuvrable enough to be able to inflict a bit of damage before it's toasted.