Two much better ways:
1) Use a pattern such as this and bucket-fill (if the white is transparency, you can easily hatch over an exist image):
 
   
Result:
 
   
You can also use more complex patterns to hatch with alternating dotted lines or the like...
2) Use the Blend tool:
 
   
To attach images see this help page.
	
	
	
1) Use a pattern such as this and bucket-fill (if the white is transparency, you can easily hatch over an exist image):
Result:
You can also use more complex patterns to hatch with alternating dotted lines or the like...
2) Use the Blend tool:
- Set the gradient typically FG to BG, FG to BG (hard edge) or FG to transparent. 
 
- Set the tool to Shape: Bilinear and Repeat: Triangular wave or Sawtooth wave .
 
- Zoom in your picture (anywhere in the area you want hatched), at least 400%
 
- Click and drag to create the gradient. - You want the initial spread to be narrow: 3 to 5 pixels (hence the zoom, so that you can move your mouse 12-20 pixels). 
 
- If necessary depress the Ctrl- key to key the gradient at 45° 
 
- Check the indicator at the bottom of the image display that tells you how wide the spread is.
 
 
- You want the initial spread to be narrow: 3 to 5 pixels (hence the zoom, so that you can move your mouse 12-20 pixels). 
To attach images see this help page.

 

 
