I use vodka. One could argue that Everclear might give better extraction because of cayenne’s oil content…but they couldn’t argue that if you squirted some vodka-based cayenne tincture in their mouth first…because they’d be crying like a little girl. :0)
1 part dry cayenne to 5 parts vodka by weight. Let it sit a couple of weeks. Shake daily. Strain and bottle.
Ditto what Doc said.  I had problems with this at first too.  I measure out my cayenne on a digital kitchen scale using the tare feature with a measurement in grams to exclude the weight of my jar the herbs are in.  I then add 5 times the amount of vodka to it.  For example: 25 grams of powder add 125 millilitres of vodka.  Example: 100 grams powder and 500 millilitres vodka (500 ml).  This is the ratio method for a 1:5 ratio tincture. Hope this helps 🙂