Centaur box

Download to full view! Its mother effing huge! But then you can see the detail!

Does anyone have any suggestions for what kind of sealer I should use for this? It has chalk on it :0 like around the box and the horse part! And other such areas! And if you touch it you will get it all over you XD I have some Plaid clear acrylic sealer "matte" and some krylon spray adhesive. I've used the plaid one before but it made everything sticky :\ so I dunno do you think I didn't shake the can enough? Or is my bottle too old? I've had both for a couple years now!

Anyway this is for sale for 50$ not including shipping!

This was done with pastel chalk, prisma color pencils, and inked with steadtler pens.