Aram, I don't have any experience decorating bows.(can I come to your class to make a bow?) :p
But, if you don't already know, sometimes markers will run and bleed, if you spray the finish coat on too heavy.
After the artwork is on the bow, very very lightly spary on the finish...let that dry, then do another light coat. After that is dry, you should be able to go ahead and spray on a heavier coat.
Krylon #1311 Matte finish in the spray dries within a few minutes, is non-yellowing and moisture resistant. It also comes in glossy.
I've ruined some artwork I've done by signing it with a marker, then spraying too heavy & the signature ran right off.
Good luck