No idea how to succeed cracking hashes

[Flomac]

Do you have an effective, simple, way of downsizing wordlists of these sizes? I think the process is called "stemming" or something - don't have much time to research into it at the moment.

I don't. Too much depends on what you want to crack. I personally use totals from Wikipedia and remove all the non-latin-letter-words. It gives me a wide variety of words that can be combined with various masks etc.