Evey, you can get nasal degongestant sprays from pharmacies and supermarkets. They cost about £4 for a tiny bottle. And it wont last long, but you can refill it with tap water afterwards which works just as effectively to moisten the mebranes to both increase absorption and make it less harsh on your nose. Not that subs are harsh to snort, they are one of the smoothest gentlest powders to snort apart from MXE, also are you grinding the pills down and chopping the clumps up into tiny bits with a blade. This too will increase the effectivenes of the administartion. You dont add the powder to the spray, unless you want to start getting really fancy in your drug adminstration. :D
I dont know why im telling you all this, its just not going to work well considering youve been on them fairly long term, it literally only works well for the first couple of days when you're brand new to them. You get a much quicker hit and a nice wave of relief/ and or opi buzz depending on why are you are taking them. You arent taking them to abuse them and get high, and for better or worse its probaly too late for you now.