Royal icing should do the trick as long as you make it to the correct consistency, it has to be stiff enough that it stays in a peak when you mix in the bowl, cover the icing in the bowl with some cling film ( I think you call it seran wrap in the US), press it to the icing and not leave any air space and leave for 30 minutes or so for the air bubbles to rise, this will help you to not get line breaks when piping. HTH
Royal icing will be perfect.
Just make sure you make it to stiff peak consistency.
You will need to pipe it onto some cellophane or something similar. Put the tiniest, tiniest smear of Crisco onto the cellophane and then wipe it off again! That's how little you need.
Leave it to dry overnight somewhere that isn't humid.
cheers, is meringue powder best or just egg white?
Just egg white.
I weigh the egg white, then add 6 x the quantity of icing sugar (eg 40g egg white + 240g icing sugar).