Any nice hot drink will help thin mucus. For the night, you might try Mucinex 12 hour. Do not break the tablets. They are time-release.
A saline sinus wash is useful for removing thick gunk. I like the larger bottles. Follow the directions. Use only distilled water to avoid brain eating ameba. The large bottles take about 1/2 tsp salt and a pinch of baking soda, or buy the salt packs that are appropriate for your bottle.
Netti pots (just a small teapot) don't provide the pressure that the bottles do. They might be OK for some, but I've had sinus surgery and appreciate the stronger wash.
This is only for mucus production in the upper areas of nose and sinuses. It will not help problems caused by reflux. I highly recommend you see your gastroenterologist to see if changing medicines will help. you may have less trouble with a different product.