Bupropion - Does Wellbutrin cause excessive sweating?

You’re not alone for sure!
I had that reaction with Wellbutrin. I was very self conscious about it

"Dermatologic
Very Common (10% or more): Excessive sweating (up to 22.3%)"

As Porsche has said, a jump to 300mg is a big jump! Perhaps your doctor could lower your dosage temporarily until you're better adjusted to the drug.
If you've been on Wellbutrin for awhile and are happy with how it controls your symptoms you could also ask about different types of medication that will control the sweating.

Normally the doctors start with 150mg and increase the dosage to 300mg after a while. As you experience sweating for 300mg once a day, my opinion is 150mg a day even though it might not be sufficient for you to fight your condition yet. Increase to 300mg later on. This is something you have to consult with your psychiatrist because everybody reacts differently.