This stop bath can be used after using standard developers either for prints or films

With line films or papers as they use very alkaline developpers :

28 % acetic acid can be done by diluting 3 parts of glacial acetic acid with 8 parts of water :

Potassium alum as an hardening effect

Ammonium chloride gives the speed effect, don't forget your films in that kind of fixing bath, it could bleach them;