I have tried everything from autoloaders to 57mm guns to derp cannons to spamming low cal HE. It doesn't seem to be even remotely possible, with even the best of games never amounting to more than 3 crits. Previously, I could use a KV-2 and get 6 critical internal hits in a reasonably good battle, maybe even in a single shot. But wargaming's massive reduction of the HE module damage, both upon penetration and non penetration, has made this 100% impossible. Most HE pens do not even deal one critical hit. I have had 10 hit, 4 pen games shooting HE with the KV-2 and T-150, never getting more than 3, two even having 0.
Setting fires is not a reliable option either, with the amount of RNG that goes into it (saving throw, module damage roll, engine shots) and the fact that the majority of the player base uses automatic fire extinguishers.
This is a problem that I think should be addressed in the next update along with the artillery missions.