Shine is one reason synthetic wigs look less realistic under bright light. The fix is to soften reflection, not coat the wig in powder.
Use dry shampoo lightly
Spray from a distance, wait, then brush through. Too much product turns dark wigs gray and blonde wigs chalky.
Wash out factory coating
Some wigs look shinier straight from the package. A gentle wash can reduce the plastic finish.
Add shape
Flat, untouched synthetic hair reflects light in sheets. Brushing out curls, adding layers, or creating texture breaks up the shine.
Bottom line
Make a synthetic wig less shiny with a light touch: dry shampoo, gentle washing, and styling texture, not heavy powder.