Butts shouldn't have skin, just fat. If you have a thick skin, then you have a "picnic". I usually score their skins and rub, but have cooked without scoring. If you are looking at fat on a butt, I trim to about 1/4"-1/8" (IF there is some thicker than that) depending on how fast I'm smoking. The faster the cook, the less time for fat to render, so trim more.
Pork is forgiving. Relax and have fun...and let us know how it turns out.
Of course, if ya want the best pulled pork, invest in some Brethren made rubs and/or sauces :)
IMBAS Certified MOINK Ball maker and IMBAS Sgt. At Arms.
And now, brethren, I commend you to God, and to the word of his grace, which is able to build you up, and to give you an inheritance among all them which are sanctified. [Acts 20:32 KJV]