How do I prepare acidic ear drops + hydrocortisone 1% and + neomycin 0.5% for otitis externa?

Acid ear drops contain 2.4 g acetic acid 30% m/m and 97.6 G propylene glycol (PG) up to 100g. In 99g of this solution 1% hydrocortisone (HC) is soluble.
but now that the doctor also adds Neomycin, we obtain another situation. After all, hydrocortisone (HC) is soluble in PG and insoluble in water; While Neomycin (NO) is the opposite.
the specimen, which is closest to your prescription is:

Neomycin and Polymyxin B Sulfates and Hydrocortisone Otic Solution USP is a sterile antibacterial and anti-inflammatory solution for Otic use.
Each mL Contains: ACTIVES: Neomycin Sulfate equivalent to 3.5 mg Neomycin Base, Polymyxin B Sulfate equivalent to 10.000 Polymyxin B units, Hydrocortisone 10mg (1%). INACTIVES: Propylene Glycol, Hydrochloric Acid, Potassium Metabisulfite, Cupric Sulfate, Glycerin, Purified Water. The pH range is 2.0 to 4.5.

from the specified pH area it appears that neomycin and hydrocortisone are quite stable in acidic middle, a pH, which we will also find at the sour ear drops. For the reason cited above, the problem will lie in the ratio propylene glycol (PG)/water. Both HC and NO must be kept in solution. So I would start with 5ml PG in which I am dissolving HC; Then dilute with 3ml of water in which NO is dissolved. Enter a cloudy on 1ml PG Add and continue to add water + NO. In total you have to obtain 10ml. Glycerin I would not add.

an alternative is the preparation of a suspension such as:

neomycin and polymyxin B sulphates and hydrocortisone otic suspension, USP is a sterile antibacterial and anti-inflammatory suspension for otic use.
Each mL Contains: ACTIVES: Hydrocortisone, 10 mg (1%), Neomycin Sulfate equivalent to 3.5 mg Neomycin Base, Polymyxin B Sulfate, equal to 10.000 Polymyxin B units; INACTIVES: Propylene Glycol, Cetyl Alcohol (0.9%), Polysorbate 80, Purified Water. Sulfuric Acid may be added to adjust pH (3.0-7.0). PRESERVATIVE ADDED: Thimerosal 0.01%.

Peculiar to this composition is the presence of cetyl alcohol. Luckily we find the concentration! I would add only three drops of polysorbate.
I suspect that the concentration PG is less critical here and here a few ml of PG are used to dissolve HC to add to the aqueous solution of neomycin and acetic acid.