For most acoustic instruments it’s just about bringing down a few bad frequencies and then letting the rest go. When you only have 4 elements on stage, once you start cutting individual frequencies too hard you’re essentially just cutting level.
For me I’d start with a HPF to about 110hz as a starting point. If there’s no bass there, don’t try to force the guitar into that role unless it’s arranged for that role. From there, grab an EQ band, keep the Q decently narrow (2.5ish), and boost around 5 db. Now start sweeping that band around 200-500 -guarantee you’re able to find something that doesn’t sound great in that range. https://amthanhthudo.com/loa-line-array Find the frequency that sounds the worst and stop. Lower that frequency band until it feels like you cut it too much. Now add a few DB back in. Widen the Q to taste.
Take another band and repeat the process for 500-2k. and again for 2k on up.
Now if you have a super thin guitar, you might want to boost some lows or mids and maybe cut some highs. But know that acoustic instruments are all over the place in terms of pickups and sound. Don’t worry about how your EQ curve looks, if it sounds good, it’s right. Feel free to bypass, and re-engage to check yourself. You’re really just looking to correct any bad frequencies and leave everything else in place.
When dealing with only 2 guitars and 2 vocals, you should be at a point where if you can get them good solo’d, they should be fine in the mix.
Repeat this process for every input. Work in a little guitar panning. Don’t comp em. and If you do. Make it soft.
Comp your vocal, but keep your guitar/vocal balance solid. Don’t have your vocal be in your face and guitar feeling distant.
Verb to taste. But in a mix like this, You’ll only need One verb and feed everything in there if anything. Keep it all in the same space.