No. 26 is a study in rapid leaps of a third or more, combined with both sudden and gradual dynamic changes (at least in the edition I’m using for this project).  Suggested tempo is quarter note=92-100, although faster tempos certainly are possible.  It’s also worth trying B-flat horn fingerings on some of the trickier passages.  Quoting again from The Horn Handbook, by Verne Reynolds:

Etude No. 26 concentrates on quick narrow slurs upward and downward. There is no reason not to tongue this etude occasionally. After achieving some speed on this exercises we might imagine that it is the horn part in a wind quintet from the classical period, and try to emulate the lightness with which this figure can be played by our colleagues on their more highly mechanized instruments. Everything becomes more difficult in transpositions, including one octave lower in F. [p. 60]