If you decide to 'go by the lake most of the way' I hope you can go up a more or less vertical face.

The lower part near Quinten is fine as one can hike more or less along the lake from Weesen to Walenstadt but behind Quinten to the Leistchamm it goes UP.
Have a look at the map as explained in the previous post.
We cheated on the Leistchamm and only did it from Arvenbühl, but going north west from Weesen we did the Federispitz. 300m lower then the Leistchamm of course - that took 'officially' about 4 1/2 to 5 hours up I think. The second or third signpost gives a longer time to the top than the first one though which is quite depressing.
Have fun. The views from up there are really something.