HI Rosie, thank you for your interest in the texture effect. If you are using soft fondant and therefore don’t need to use to much pressure if the cake is a soft texture, then it would be fine to do this on the cake. You can also achieve textured effects with royal icing (or frosting) and then colouring it up after it is dry. I used that technique with some stone walling on a castle cake by using a cocktail stick to create the marks and grooves and then applying various colours of dry powder when it was dry. I then whooshed that about it the same way, using a bit of water. This is the texture: 
This was created on fondant without damaging the cake. This was a mud cake which is quite firm and had chocolate ganache underneath which had set, so enabled me to apply a small amount of pressure
I do hope this is helpful in some way Rosie, please ask me any more questions if you have them :) Good luck with the Dinosaur! I am looking forward to seeing it :)
Love
Fiona
xx
'It Always Seems Impossible Until It is Done' Nelson Mandela http://www.facebook.com/CakesByFifi
