Hi Katie
Just my 2 cents
As you know Krylon makes many types of paint,Auto Enamel,Latex,Lacquer,etc. and they all have a different base just like Shellack as it's own base, water,mineral spirits,etc. I would not mix them in different coats.
I would use a wipe on ploy to give it a hard finish coat and a flat-satin finish.(3 coats)
But that's just my 2 cents ,If Jerry sees this post maybe he will jump on it and give a hint or two how to use both types .(shellack)
But as you know they use spar shellack on boats and it's hard and will last a long time if it's done right, also think about the epoxy coats, takes a long time to dry but will stand up to abuse.
Bj