I heard you should not use mouthwash right after brushing. Is that true?

Yes, it is better not to use mouthwash immediately after brushing. Surfactants in some toothpastes can react with the antibacterial ingredients in mouthwash, reducing its effect or causing tooth staining. Use mouthwash about 30 minutes after brushing, or rinse your mouth thoroughly with water first. Mouthwash alone does not remove plaque, so it cannot replace brushing and should be used as an aid.