Hum and muddy sounding guitars

Almost every EQ FX will have a high pass capability.

It's standard practice to run a high pass on any source that doesn't have a fundamental down in the sub region.

In your case it's not so vital because you are recording direct... it's more common when recording in a room because the room will resonate below the source "instruments" fundamental and ADD low energy content to your recording... which you can then filter out using an EQ.

It's certainly possible for an amp sim to synthesize extraneous sub content... either by mistake or in an effort to mimic the sound of a mic'd cabinet (in a room).

In either case you simply set up a high pass and then adjust the node up and down the frequency spectrum while listening for the difference between lo end noise and your instruments tone. Cut out as much noise as possible while preserving the character of your tone.

I think it's far more likely that you need a bandpass filter in the 150Hz to 400 Hz range... that's the "mud" range.

Of course as suggested you can employ the best filter by arranging not to play too much mud in the first place.

If you still end up with muddy tracks you can try deep cuts with band pass filters and hard panning to separate the sources of mud to make them seem less muddy.

You don't want to stack up a lot of energy in the 150Hz to 400 Hz range. It makes a mess.

best regards,
mike