Best way to achieve a solo boost

Depends on your style... sometimes a midboost is enough to cut the mix.
+3db Volume increases to much bass sometimes, imho.

Live I've been putting a Boost in the Effects section (post amp) and using the lock feature to keep it there. So whatever profiles I wander into, it's there and footswitchable. I do this because I am still new to the Kemper and still love having all those sounds to try out on the fly if I like.

I use a -2 setting on my volume pedal
And raise as needed.

OP, that's how I would do it.

Live, I use my guitar's volume knob.

That's no more daft than using something this versatile like a foot controlled mixer fader

It is likely a personal style thing - even with high gain rigs, I use a little less gain for chords, and a little more gain for solos, and the guitar knob is something I can use away from the pedal board. You have your rig set up to use a little less gain for solos (one string is less signal than many). I have friends who NEVER touch the guitar volume knob - I'm always using mine.

Part of what I like best about the Kemper is the organic way it reacts to touch, volume knob changes, pickup selection, and different guitars. AND another part is that it can do hyper gain skull crushing distortion, at the push of a button.

Quote from paults

It is likely a personal style thing - even with high gain rigs, I use a little less gain for chords, and a little more gain for solos, and the guitar knob is something I can use away from the pedal board. You have your rig set up to use a little less gain for solos (one string is less signal than many). I have friends who NEVER touch the guitar volume knob - I'm always using mine.

Part of what I like best about the Kemper is the organic way it reacts to touch, volume knob changes, pickup selection, and different guitars. AND another part is that it can do hyper gain skull crushing distortion, at the push of a button.

Same here, and fully agree.

There's no single way to do it. Personally for a loudness boost I use a 3-5 dB louder rig in performance mode although I also extensively use the volume pot.
Others prefer a boost or neutral EQ post amp.

Agreed - whatever works!

Since I use the KPA, I got used to operate the volume knob. Before that I've hit the boost on my OKKO Twinsonic.
I find the volume knob quite convenient, I've to admit. This gives me more control to fit in the mix of the band. I've tried also storing three different volume levels of a specific rig. But it never was really fitting the situation, so I decided that fully grown male individuals (c) better use the volume knob - besides operating a Telecaster.

I think everyone was just offering what you asked, and it shows that we all have our ways of achieving the boost. I find that feeding the pedal gives me dynamics throughout the tunes all night. I do switch for to a rig for the lead in some songs but still may have the dynamic ability in the pedal. Ya never know how hard or heavy handed your drummer may be each night. That's why I will utilize both pedal and pot!! And of course grimace at the sound tech in the case I don't see any hotties throwin their bras and panties at me immediate after my mind blowing solo!!

I use a locked EQ boost in the X slot - with assigned IA switch so it's always there (1010, UNO4Kemper). I also use the volume pedal so I can "put my foot on the gas" for a spot solo, fill or juice the main riff up before the vocals come in - I like having both options so I don't loose my balance tap dancing!

For sounds with heavy gating and gain, I think you are on the right track with a post-stack boost. Any substantial volume boost before the amp would likely make the guitar harder to hear, because of the additional distortion it would add.

Are you using a sound engineer? If not, you might need more than a 3db boost, if your solos are to be at a featured volume.

I like the Metal EQ before the amp, with the Mids boosted way up around 400, and the High and Low knobs rolled down - however, I'm really lazy and hate having to switch pickups, so this is mostly just to approximate the neck pickup's tone and then push the amp section a bit harder.

...come to think of it, my neck pickup's been broken for about a month and I haven't even bothered fixing it. Yeah, "lazy" is definitely the right word.

If you use Andy's Profiles (TAF) you will notice, that he normally puts an EQ into the KPA's X-slot to boost the signal, on some profiles + 5dB. I think that's the best way to boost a signal and if you change from rhythm to lead you can use a diffrent EQ-setting, too.

Personally I use -like many others- the volume knob of my guitars, especially with strats there's a lot of different sounds you can create. I also use the "violin-swell" quite often.