Don't Exclusively Rely on Freeware Plugins
The plugin is CPU light, easy to use, and initially free to use. Not only does it include professional sounding cabinets, an ever-expanding library where you can purchase new cabinets from inside the plugin (the average is about 6-8 EUR by the way to it's really not expensive!), and simulation of the Poweramp section of ahead in every way you can think - but you also have access to mixing 4 cabinets and Mic's in every way you can think, AND it includes Studio Grade processing units for Compression, Reverb, EQ, and an Exciter all built into one plugin.
Two notes Audio Wall Of Sound Plugin is a great alternative to mic'd up cabinets, and give you unlimited access to the worlds finest collection of impulse responses
Multi-Band Compression to tame that Low-Mid range
Possibly one of the most underused processes on Guitars (and in general) is Multi-band Compression. Let me explain why this is better in a lot of cases than EQ as quickly as I can.
EQ is typically for shaping the sound of the recorded source and removing unwanted frequencies / boosting wanted frequencies. When applying this to guitar, your tone can quickly become saturated with several notches, and mixed with ear fatigue, your tone will suffer very quickly especially when used on the lower mid-range of your guitar tone. This technique is, in short, a one-stop-shop to a thin and wispy tone.
So, this is where Multi-band compression comes in. When you don't want to eliminate the frequencies because they're only sounding unwanted on certain parts (think palm mutes, higher strings, sustained notes, and chords, etc.) and they just need taming on those certain parts; Multi-Band compression helps to compress that frequency range in particular, for that particular more low mid-range heavy part, and still manages to retain your overall tone with no sacrifice.
Don't focus all your time on the Higher-Mid range
Now, I'm not saying it's not an important place to concentrate on - trust me I hate that frequency range as much as the next audio engineer on guitars, but it's not the one place you need to focus on.
Personally, I try to attenuate between 2Khz and 5Khz with bell peaks which in turn pull down other harsh frequencies with them. Try to use your ears to figure out which ones are 'whistling' or 'ringing' and attenuate in small increments till you're happy. But this isn't the only pace an EQ can be very powerful - High Passing at 80hz will eliminate rumble and help clean up your overall mix by allowing your sub frequencies from the Bass Guitar, Lower tuned shells from the Drum Kit, Room Mics, etc. to shine through.
This is my typical guitar EQ across the board - but it does change between every project to make sure you use your ears! Notice I'm only making small changes to the spectrum; if you find you're having to make drastic changes, go back to the source tone and try and improve there efore EQ'ing again.
Make sure to focus on is frequencies that stand out too much on your tone - usually in the low-mid range that can make your tone 'boxy' or 'woofy' but, that being said, without this lower midrange your tone will sound shrill and way too thin, so a few basic rules to follow are:
Small Cuts (around -2db or -3db), with a Bell Q of about 2 to 3.
Use a bell peak like described above and boost around 6-7db - move across the frequency range of the EQ, and when you find somewhere that pokes out too much, then cut by a small amount.
Don't Cut everywhere - try to listen in the context of the overall mix un-soloed, and figure out where frequencies are clashing - then when you cut them they will make a genuine change to your mix and your tone rather than just blind mix changes.
Lastly and most importantly - A/B Comparison. I can not stress this enough, any time you make a change to your tone using EQ, listen to your change, then Bypass the EQ, then listen to your change again - and decide if the cut or boost helps your mix and the tone overall!
Get yourself some GOOD accessories
Hosa Technology make a cabe called the Edge series i can't recommend enough - not only is it extremely high quality, but it won't break the bank either!