If you could glue your hand together and to the gun it would create an effective grip. Yeah I know it sounds over the top and not the most practical technique to rely upon defensively.
What I have noticed is depending upon the weather, my skin dryness or hand cleanliness it make a significant difference it how well I an able to maintain a solid grip. Where I notice it most is in my support hand. If it is dry or my skin is very dry my support hand will slip slightly where it contacts my strong hand. Frequently now I have noticed how as my hands get gummed up with powder residue during a extended range session my grip improves. Shooting in the rain, I love it. My grip is definitively better when my hands are wet. I just think I have inherently dry skin.
The other day at the range I was experimenting with grabbing some dirt or grass and dirtying up my hands. The moisture from the grass made a positive difference.
For a while there I found myself searching online for some sort of product I could use to make my hands a little stickier. I just don't want to become dependent on something that would not always be there.
Thoughts?