if you don't want to use morphing (as it may be set for something else), I'd suggest using the Pure Boost in the X slot after the amp. It's volume boost goes up to "5" (whatever that is) and provides a nice solo boost on any slot selected. Takes up one Effect button, wherever you'd like.
that always sounds great - I just figured out that two pure boosts work best for me - one in the A oder B slot to fire up the amp a bit and one in the X slot for the boost, you can link them together with the remote and it will open up great, full and sustainy