Im planning to cosplay Terezi Pyrope from homestuck and have cosplayed Karkat Vantas
But the problem is the facepaint gets everywhere
Is there a way to seal it without using hairspray (I'm not allowed to use that method)

Ben Nye final seal is amazing stuff!

Vaseline maybe you can buy a sealant on www.larpinn.co.uk

I really really recommend Ben Nye. They do a clear setting powder which is apparently very good, but I've never used it myself. I have used the Final Seal, though, and it's amazing! You can buy it from eBay or I think Screenface do it too? They're a shop down in London but I'm 80% sure they have a website you can order from for delivery

When I do my troll cosplays I use both the clear setting powder (You'll know it's working cause it makes your skin tighten up briefly...) AND the spray and my stayed on the whole night at a sweaty disco.

So yeah it's definitely worth investing in!