You can take small amount of blood from wherever you can. Any finger from left or right hand, it will be OK.
And what do you mean by "dead skin"? I am afraid I do not understand that part at all.
Here is my suggestion for all of you who are terrified about piercing your skin: go to your pharmacy store, and buy that little needle gun that diabetics use when they check the blood sugar. It is small aparatus, it has a needle on a top which is driven by a small spring, when you press the button, it punctures your skin in a fragment of a second. You barely feel anything. It has settings for how hard you want it to strike.
After all, if fear of puncturing your finger is stronger than your will to dedicate to Him, our Glorious Creator, Father Satan, maybe you shouldn't waste your time with dedication after all.
Hail Satan! Forever!