Hello.
I attempted today to use the new select and mask tool in Photoshop. When I started to refine egdes around the hair, alot of "pixels" came up around the hair. What should I do?
IMO Select and Mask is not magical it can not perfectly mask stray hairs. You need to work on the mask and blend in the replacement background. Try different layer blending modes and layer stacking orders. You may need to fudge some areas. A perfect extraction is not always posible. There needs to be good contrast between the background and subject for a perfect extraction. Good contrast is not something that exist in all images.
Ther are also many turorials online on how to use Select and mask. https://www.google.com/search?q=Photoshop+Select+Mask+tutorial&oq=Photoshop+Select+Mask+tu torial&aqs=chrome..69i57.23111…