The lines look a bit , did you use a stylus?
Some advice (if you have not already done already):
1) is to use different layer for different shades.
2) Many times, using mask is better than eraser, as it is reversible.You can always Apply mask later.
3) Use the rotate function and scale, to get the angle/Size to apply a brush stroke. Especially useful for line work.
Used pen for Effect line and Marker Fill in mono pen.
Yeah used Layers for the different parts, started out in Layer 1 with making the shape, Layer 2 for stronger lines, Layer 3 for details and Layer 4 for smaller details that I am yet not sure if gone use.
Ok, thanks, masks that I need to look more into, I often use eraser .
Yes, scaled that one, started a bit small, then scaled it to add more details.