I haven't done much in the event (just one wave so far) because I'm levelling up my light tanks and arties first (far as I know, there's no daily free auto reset so there's no rush to do it immediately)

Light tanks + Arties against armoured train with all those accuracy enemies seems an awfully brutal trial though.

Still, 500 cores to reset to get 5 Han's on average (more if you're better) is probably a better deal for eliting a 5-star tank than spinning the premium gacha for them (around 1.6k or so cores on average per 5 star tank if there's no increased rate event going on vs around 1k cores to get 10 Hans, though you won't drown in gobs of 4-star girls), and that's before taking into account being able to CHOOSE what 5-star to boost up as opposed to completely random.