Hi Diamond,I use the ‘external’ glue you get from Bunnings, play with it a little bit before you do your piece. One has a ‘expandafoam’ reaction to it ...

Had a kids party yesterday in a park so I grabbed some white rocks from landscape & oil pens from the tool shop. The kids had a ball decorating rocks ...

Selley’s is a great brand of glue just don’t over use the glue. I’ll pop into Bunnings tomorrow and see what the one I use is called. Cheers!