You can go straight up Anderson Road- the fireroad that leads up from behind the Essentials freeride area past the quarry- and that gets yo up to spooky fast… But it’s horrible tbh! Do Pennel’s and the singletrack climb, much nicer. Your route is pretty efficient really.
I think you should be able to view this…
http://app.strava.com/segments/2647008
That’s the Fort descent, from the back of the green route down to Janet’s Brae (there’s a bit cut off at the end but it’s easy to spot from the Brae). It all gets a little bit vague after a minute or so, there’s a couple of likely looking options but as far as I remember you just have to keep left.