UPDATE: Like 50 people have said "should have used a bald cap!"  I am aware that bald caps exist.  On the day I did this cosplay, it was almost 100F outside, so I chose to just shave my head.  It made the makeup application easier, and I was able to stay just a little bit cooler throughout the day.  I shave my head a couple times a year as it is, so it's not like it was a huge sacrifice for me to do it here.

This was our first attempt at using the liquid latex method of creating wounds/scars.  It took about 45 minutes to apply the makeup and about an hour to remove it.

Makeup materials used:
Liquid latex (1 bottle, but 2-3 could make it even more pronounced)
Foundation (just pick one that matches your skin tone)
Medium red, dark red and black makeup (for the open wounds)
Yellow makeup (for evening out the tone and adding a bruised/sickly look)

Costume materials used:
Generic Deadpool zentai suit
Combat boots (make sure they're comfortably broken in, since you might be on your feet for a long time)
Assorted holsters, belts and prop weapons (use as much or as little as you want, depending on how much you want to carry around)

Music:
KMFDM "Light"
EpiPony "Corruption of Harmony"
PrinceWhateverer "Shallow Naivety"
ShredGuitarBrony "Sombra's Door Metal Remix"