Nasal rinses are super, super useful. You can put your regular dose of nasal spray into the bottle as then it gets right up into the sinuses. It's CRITICAL to use boiled, cooled water as otherwise any bugs in the water can cause big problems, even death. Boiled water kills any bugs, obviously.
It's also worth seeing an ENT to get your sinuses properly checked. It may be a physical exam or a scan. An ENT massively improved my sinus issues.