A few further points:
—Stenzler's Grammar has never been used, as far as I know, outside the German-speaking countries
—Many have used (both as students and as teachers) Coulson's Teach Yourself Sanskrit, possibly integrating it with Whitney and Speijer's Sanskrit Syntax
—In my personal experience, I used (both as a student and as a teacher) Ashok Aklujkar's An Easy Introduction to an Enchanting Language
—If you want to have a deeper glance of the issue, you might want to get in touch with Prof. Iwona Milewska, who is —among many other qualities— also a refined scholar of the history of the didactic of Sanskrit (I might send you her address in case you need it)
Best wishes for your research!
elisa freschi