It's pretty straightforward going up Grasmoor from Coledale Hause.
If you have a look at the 1:25,000 map for the area, you'll see a path, marked by a black dotted line, breaking away from the green right of way route, about 300 or 400 metres south of the path junction at Coledale Hause. Take that path, which skirts around the edge of Grasmoor above Dove Crags, up to the summit of Grasmoor. From the summit you can then follow the path that heads south westerly direction towards Crag Hill, where you'll meet another path junction indicated by a spot height of 722 on the map.
