A lot of the mixing is going to be eyeballing it. Pick a shade close to what you want and then add a bit of whatever colours. Using black or white isnt the best way from what I have found to make the paint darker or lighter although they will work. Instead I use darker or lighter greys. If you are looking for a particular colour combination google is the easiest way. Having said that it can also be frustrating. IPMS Stockholm has an incredible paint chart and advice for various subjects. It has some paint mixes.
https://www.ipmsstockholm.se/home/urbans-color-reference-charts-part-i/
Other than that all I can advise is experiment. BTW I use small sot glasses to mix my paint and any left over I store in repurposed tamiya bottles or eyedrop bottles. Lable them and keep like regular paint although they do not last as long in my experience.
James
One handy mixture Laura provided here at the beginning of the site is instead of using black to paint a cockpit or aircraft or whatever, add a bit of flesh to it. It still looks black, just not so dark and you can still use black to shade it.
Hope that helps.
James