When in doubt, just use -ko
Japanese Language
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-ko for physical items, -tsu for abstract things.
Hell, I'd argue most Japanese just use -ko in every day life except for the important counters. 羽、匹、本、冊、日、月、年、枚、円、人/名、戸、階。 Those are the ones I believe are necessary. Almost everything else can be replaced by -ko or -tsu.
Interesting
I find nothing helpful except exposure. Reading and hearing it cements the oddities of counting.
Yeah, it's hard. I feel like it got a little more comfortable when I stopped trying to stress about memorizing them. But it is probably good to go ahead and do flashcards for 1-10 things and 1-10 days.
Once you get used to a few counters, then learning a new counter is like learning a word. You can kinda feel when rendaku might kick in, or ichi gets shortened, etc.
Even still, it's just hard. I know I've seen a few videos on YouTube or TikTok of people just counting, or doing songs with counting. But unfortunately I don't have any on hand to link.