I will edit and write more these days
First I look at the things that are more important when I start to build the song. The solo or the rhythm. Then I analyze the sound and start from that impression.
Most of the time i cut a lot from the low end on the solo guitar track and maybe add a little around 7-8 kHz. It helps to cut trough the mix.
Some times I cut around 3-4 kHz because I hate these frequencies on my solo guitar sound.
Also I don't compress the solo guitar. Most of the time I play with hi-gain settings and it sounds already compressed.
Here are my usual crunch solo setting with Aradaz Crunch Amp.
I'm using GClip to add some more gain to the input. My hardware pre is my Line 6 Tone Port GX
You can see the EQ and my Delay and Reverb settings too.
This is the chain patch for Reaper
I record two rhythm guitar tracks and send them in a group. Then some very soft compression and maybe an EQ.
I use this rule: If my main solo is more in the middle range I cut the rhythm guitars around 500 Hz or around there.
If my solo is scooped with a lot of highs I use round and full - middle range sounding rhythm guitars to fill the spectrum.
Here is a VIDEO with these settings