The two ways I've really liked (either alone or both) are a TS in front of the amp (same way I did it with a physical amp) and a neutral/flat boost of a few dB via basically any method that works (CS to turn up the amp, cab, or output level; un-bypass a null filter block; etc.).
I like having both available because they obviously sound different. A TS or Klon works really well for this because they both take off a significant amount of low end (which "eats up" a lot of your headroom) and have enough headroom to boost enough. Depending on how they're set, when you turn it on, you get some headroom back (from driving less bass), which essentially reduces the amp saturation, then boosts into the amp (and adds its own) so the sound doesn't really clean up...and you typically get a level boost from the amp. It kind of "focuses" the saturation you're getting more in the midrange and makes it louder.
The other way I like doing it is turning the amp up louder (more gain) than I need/want it and having my "full on" tone set up for the guitar volume on ~9. If you don't use a treble bleed, that last little bit on the volume pot takes off a significant but not huge amount of high end, and this happens at least a bit even with the tone control(s) down. So, when I need it, there's a small saturation and brightness boost right there on the knob.
Right now, I'm just using the TS and setting my amps hot, as I find those more valuable overall. But, that's also because I'm waiting on some Loopi TRS dual switches to ship from the other side of the world (figured I'd try them before a MIDI/FC controller because they're cheaper and wouldn't require me to buy a new pedalboard).
I might start another thread about that, I have that issue a fair bit but I don’t fully know how to describe it. I’ll post a preset tomorrow.
