Its easy to rush a thru tenon joint and end up with a sloppy fit. I have often approached the method of work with too much confidence, after all its just a square block going in to a square hole right?
We left off having finished the layout and scoring of the mortises. Personally I would rather fit the tenon to the mortise. I find it easier to sneak up on the fit by filing or paring the tenon. I find it difficult to keep the walls of the mortise square with the face if I start having to adjust the mortise. This is my preference, so I start by cutting the mortises.
I use a shopmade slot mortiser to cut them, but a plunge router and template is more than adequate. Dry fit your shelf into the dado and use a marking knife to mark the outline of the mortise.
Now we transfer the knife lines to the face and layout our tenons. I prefer to mark the waste portions with pencil to help myself remember what SIDE of the line to cut on.
I use two techniques to get cut the tenons out. A Ryoba saw for the outside cuts and for the two interior the familiar coping saw and chisel routine.