thanks a very good tip
I would recommend investing in a Marshalltown M43 Worth it's weight in gold for grouting. Pro tip: Use a dry powdered grout and mix yourself. This chemically cures, rather than air drying with the ready mixed stuff. Apply with a Marshalltown M43 grout trowell. Allow to go off a little, then attack it with a tightly rolled damp rag, and keep rag well rinsed in water. Eventually buff off residue with a dry rag.
Sponge over it at an angle, that should stop it from coming out.
I can tile perfectly well but when it comes to grouting I tend to wash the bloody stuff out too quickly