You can somehow substitute a spot meter with your light meter if you measure at very close distance to spots you are interested and close to. In the shot you showed you'd point it both at the rocks in front of you and into the sky above you. You'd measure the sun lit and the shady area of the rocks to get some idea how bright these are in absolute terms and how they would register on your film.
In the end, all the spot metering won't help you since you can make only one exposure per frame and you can hardly change the contrast of slide film. It only tells you whether a shot can work or not or whether a GND filter helps.