How do you exclude branded keywords from Google Shopping campaigns without hurting performance?

• Do you use campaign-level negative keywords?
• Do you separate branded and non-branded Shopping campaigns?
• Have you seen any impact on ROAS or conversions after excluding brand terms?
• Are there any common mistakes to avoid?

I'd love to hear what has actually worked for you, especially if you're managing larger eCommerce accounts. Real-world experiences are much more helpful than generic advice.