Question: Do you condition your existing biohair (if applicable)?
Slick, freshly conditioned biohair is the enemy of wig grippiness.
Your wigs will stay on much better if you refrain from excessive conditioning, particularly at the perimeter of your hair line. Most conditioners have waxes or silicates in them to make the hair feel slick to the touch. This may help you get a comb through it more easily – but it will also cause anything you put on that hair to slip and slide around more than usual.
For the record, I only wash my biohair about 2x a week and only apply conditioner to the tips. Not only is this way healthier for your scalp, but it helps the wigs stay in place better.
Along those same lines, applying a little stiff hair gel to the front and nape of your biohair and allowing it to dry before applying your wig will also help it stay in place better.
If you do not have any biohair – like if you have alopecia universalis or something like that – then you may need to use adhesive tape on some of the monofilament features in lieu of a grip to keep the wig in place. The red tape from Jon Reanu is made for mono tops, the blue tape is for lace fronts. You’ll also want to pick up some Lace Let Go to remove the adhesive without damaging these delicate cap features.