Open your project in DaVinci Resolve 20
Go to the Color page
Select the clip you want to isolate
Open the Magic Mask panel
Choose the Magic Mask mode
Select Person or Object
Use the brush to paint over the subject
Add strokes to refine the selection if needed
Subtract strokes to remove unwanted areas if needed
Click Track Forward to analyze the clip
Click Track Backward if needed
Review the mask across the full clip
Refine the selection with additional strokes
Adjust mask softness, clean black, and clean white if needed
Invert the mask if you want the opposite area selected
Use the mask with color corrections, effects, or grading nodes
Enable or disable the mask preview to check the result
Save your project when finished