Weird marks on my art?

[shorte85]

Hi, was hoping someone could help me? I am trying to get a smooth "3D effect on text" in gimp. I am following a tutorial, and it has me create a paint brush by copying a selection which I did.... Once I created my path using a text (font) to trace and then stroke path so that way the paint brush I created is used.

However, instead of it being smooth and pretty like the tutorial... I am seeing weird marks, which I uploaded the screenshot so you can see it too.

Could it be due to my brush settings not being quite right or is it something to do with my laptop graphics?