How to get that orifice looking right?

As these rainbows are going to be shot out from a human orifice, I need to build up the wall to that the whole wall and opening look or resemble skin.

I started with some plaster that I had and began to mix it up....

I managed to mix it completely wrong that it started to set almost immediately, so after rushing and shoving as much as I could on as quickly as possible, I realised that I needed more.

I also wasn't too clever about getting the right second load of plaster, which came out wrong colour and texture but Im on a tight schedule and it just had to do.

You can see how grainy and sandy the material is but "art is made up for lots of mistakes". - I think some famous artist once said..

I also added a few rainbows, trying different colouring techniques and materials and experimented on different paper to see what would stick on better using wallpaper paste.

I found that felt tips ran and crayon, pencils, watercolours and acrylics worked well and printing paper seemed to hold pretty tight.