Grouting Buttons to a Frame

I have had a go at grouting buttons onto a frame.

I have a large red frame, took the backing off the frame to protect it. I then sanded down the red paint to hope that the grout will stick better.

Using my palette knife I put a thick layer of grout onto the frame...

I then pushed all different sized and coloured buttons into the grout and left to dry. 

I am waiting for the grout to fully dry at the moment but I hope the grout sticks to the frames surface okay, if it does not I will have to think of a glue or lacquer which could cover this.