Create a new image, go to "Layers, Channels & Paths". Create a new path by clicking on
. Use
to modify the points.
Select a brush (Circle 07 should be good):
Select a color. Not too bright (R:127 G:31 B:0 gives a nice dark red). Click on
to stroke the path:
Select a fuzzy brush (in our case Cirle Fuzzy 07):
Select a brighter color (I used R:255 G:63 B:0). Stroke the path again:
Source:the Gimp User Group