A rough key usually traces back to the shoot, not the software. Before you slide a single control, look at the frame and name the problem. Uneven green, a hot spot, or a shadow each need a different fix.
Zoom into the worst edge and ask what is wrong. If the background is patchy, no key setting will ever look clean. If only the hair is noisy, you likely have a problem you can solve with a second pass.
A blotchy green comes from uneven light or a wrinkled cloth. The key can only remove one narrow range of color at a time. If the green drifts from bright to dark across the frame, raise the tolerance and you lose the subject too.
A soft garbage matte can crop the worst corners and save a shot you would otherwise reshoot. Blur the green in a duplicate layer to average the patchiness, then key that blurred plate. This trick smooths a screen that was lit by hand.
A thin green line along a shoulder or jaw means the edge is catching colored light. A small choke pulls the matte inside that line. Add a touch of edge blur so the correction does not look carved.
Spill suppression removes green that bounced onto the subject. Keep it modest, because heavy suppression turns skin gray and clothes muddy. Use the shot itself as the judge, not the number in the field.
Most rough keys are uneven light wearing a software problem as a disguise.
Hair is where weak keys fall apart. A key that works on a solid shirt can leave a sawtooth mess along loose strands. Sample the key from several green patches so the matte has more to work with.
A second, softer key pass just for the head can help. Some tools let you combine a tight key for the body with a gentle one for the hair. Blend the two until the edge reads as one clean shape.
Setting up your first green screen takes a frame, a cloth, and some patience. Here is the order that keeps wrinkles and hot spots out of your shot.
Lighting a green screen evenly is a metering habit, not a gear list. Learn to wash the cloth, match the bulbs, and keep your key light off the wall.
Distance keeps a green screen key clean. Stand your subject several feet from the cloth so shadows and color bounce never touch the shot at all.
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