Actually, some Altec drivers did use water-based dope. One can see from the references below that different products (only some of which were Moyen products) were employed in specific applications. Factor in that these references were guides for a single (later day) point in time and the listed products were not necessarily all historically available for the duration of Altec doped cloth, and the question of there being a "right" dope for general purposes becomes moot.

Inspection of a wide variety of doped Altec surrounds from varying periods easily exposes the differences. The latex variants have less mass and appear more as a continous surface when dry. Latex dope is much easier to apply, and generally only takes one coat. It doesn't run or sag either.

One has to assume they had a reason to use different dopes on different drivers...

http://replay.web.archive.org/200506...f_recone_1.pdf

http://replay.web.archive.org/200506...f_recone_2.pdf

Added
The absence of the typically runny 414/416s from the above references suggests yet another variant, though we'd need the missing reference to know what it was.