Hi there,
I actually have the same husk supplement purchased:
To start off a small teaspoon in a cup of water worked decent for me, make sure you drink it quick, but ofc not too quick since you have gastritis. Remember fiber requires more acid to break down so don' t just throw it in there.
If you really wanna go #2, I recommend Flakseed powder, it's an "colon irritant" as my PCP described it. Essentially it tickles your intestines to get you goin, here's the one I used:
Aloe vera juice also helps loosen stools, also extremely helpful for treating Gastritis:
