Of course possible. Just the basics as a starter. Using the gradient editor is a bit of a pain, there is no undo (that I know of) If (when)_ you make a mistake usually better to start again.
However it goes like this - 2 minutes duration
That is a basic FG → transparent → BG gradient. For anything more complicated I usually fall back to an old RobA script sample-gradient-along-path.scm from here: http://www.silent9.com/incoming/scripts/ There is also a similar function in the gmic plugin.