The best thing I ever did for decongestion was to get outside and start wearing a mask during the winter. The air entering my nose is clearer and warmer, which causes less mucus production. The mucus that is produced is more likely to drain, rather than sit around thickening and waiting to be blown out. I wish I'd thought to wear a mask while out when I was younger; could have saved myself much suffering waiting at the bus stop and during the subsequent schoolday.