Grouting advice please

Hi
Before I make a complete mess I would really like some advice on the best way / tools ect to grout in small stone / glass mosaic tiles on the bathroom wall, what makes it appear more difficult is that the stone tiles sit proud of the glass so I have an uneven surface to wipe clean.
I'm told that the stone tiles need a sealer so the grout does not bond if so what sealer? The more I look at the wall the more of an arduous task the grouting becomes.
The mosaic tiles are a mixture of cracked glass and white hard stone 16mm squares.
Thank you all