I am going to use Drysol. How long do I use it and how long do the effects last?

From Drugs.com:

How should I use Drysol (aluminum chloride hexahydrate topical)?

Follow all directions on your prescription label. Do not use this medicine in larger or smaller amounts or for longer than recommended. For best results, apply the medicine only at bedtime when you are less likely to sweat. You will need to leave the medicine on your skin for 6 to 8 hours.

This medicine comes with patient instructions for safe and effective use. Follow these directions carefully. Ask your doctor or pharmacist if you have any questions.

Wash and completely dry the skin before applying aluminum chloride hexahydrate. You may need to use a hair dryer to thoroughly dry the skin.

Use the applicator provided with your medicine. If your medicine does not include an applicator, use a cotton ball to apply the medicine. Apply the medicine evenly and allow it to dry into a thin film. Use a hair dryer on a cool setting to dry the skin if needed.

After use on the underarms: Wear a tee-shirt to keep the medicine from rubbing off onto your bed linens.

After use on the hands or feet: Wrap your hands or feet in plastic wrap and cover them with cotton gloves or socks. Do not tape the plastic onto your skin. Leave the gloves or socks on while you sleep.

After use on the scalp: Wear a plastic shower cap to bed to keep the medicine from rubbing off onto your bed linens.

When you awake in the morning, remove the clothing or plastic covering from the treated skin areas. Wash or shampoo the skin thoroughly, and towel dry. Throw away the plastic wrap do not reuse it for additional applications. You may rinse out the plastic shower cap with water and allow it to dry completely before using again.

Keep using the medicine for another 2 or 3 nights until you notice reduced sweating. After that, you may need to use aluminum chloride hexahydrate once or twice per week to control your condition.

Store at room temperature away from heat or open flame. Aluminum chloride hexahydrate contains alcohol and is flammable. This medicine will evaporate quickly when exposed to air. Keep the bottle tightly closed when you are not using the medicine.

https://www.drugs.com/mtm/drysol-topical.html