Applying the grout wasn't too difficult.  I used a soft sponge to spread it across the mosaic.  It was spread across the surface covering the tiles as well, rather than trying to fill every individual gap in.  I then wiped it over several times until all the cracks had been filled.

As it happened I needed two mixes of grout.  I also applied a layer round the outside of the mosaic to both keep the tiles in place and to make sure the whole thing was completely waterproof.

After grouting I went over the tiles with a damp sponge to remove any excess grout.  I then left it for a couple of days to dry before cleaning the tiles to give them their shiny look you see here.

  Well?  Masterpiece or what!!! 

  Not bad for a first attempt!