Remember that it's not always necessary to fill a sonic space. Whilst I use some of the above techniques in my trio setup, sometimes it's just nice to hear the guitar solo breathe a bit.
Don't always assume if there's a space, you fill it, judge it on a case by case basis.
A classic case of "leave some holes, some music might fall out"
Don't believe? Watch Pino with John Mayer trio, loads of space, he nails it.
Si