My Spanish is mostly Rioplatense-based so I typically use “ustedes”. I do try to memorise the verb conjugations for “vosotros” though, mostly for reading/listening.

Then for the singular I typically use “vos” most of the time, and “usted” in the formal. I don’t know exactly the rules; frankly I simply hack it through Portuguese, if I feel like I’d call the person “o/a senhor[a]” I use “usted”, otherwise I use “vos”. But just like the above I try to memorise the “tú” conjugations.