I have a couple of different brand or styles of disconnect tools; usually one type will work where another type wouldn't.
A a lot of times you do need to blast the crud out from around the spring with spray carb or brake cleaner.
And make sure that the hose isn't pressurized- that will hold a spring and keep it from expanding.
If your tools don't work, try this before cutting a hose. On rare occasions over the years I've run into a Spring-Lock (Ford's name for the AC or fuel disconnect) that wouldn't budge; with any of my tools and even after cleaning, and even after cursing at it. I was able to disconnect these oddballs by taking a small piece of thin shim stock, deburring the straightest "working" edge, and rolling it into a cylinder. I used an open-end wrench to push the cylinder into the coupling, and it's tendency to unroll pushed the spring back whereas the specialty tools wouldn't.
If you get desperate, it's worth a shot.