What's a tip in page? Well, we simply cut a piece of watercolour paper to fit inside and attach it with washi tape at the outside edge. The watercolour paper will take all the wet media, but you might have to be careful what you do with the other pages if you get the weekly planner journal from Moleskine (as suggested), because that is quite thin paper...try gesso.
The edge of the book looks really cool if you can source a few different colours of washi tape...but be careful....collecting washi is very addictive....ask any DLP (documented life project) practiser!