I agree with Negrogesic on this one. Pretty much any drug is going to produce a rebound effect upon cessation of chronic use. The good news is that the withdrawal from Quetiapine (Seroquel) really should not be too bad. The worst part that comes to mind would be a little bit of insomnia. You're using this drug for sleep and you're probably pretty used to "taking something" in order to get a good night's sleep and it can be hard to figure out how to sleep without that "something". I am the same way with Cannabis. I'm not an insane smoker, maybe a gram a day, but I lose my appetite and have trouble sleeping if I don't use Cannabis. Really, we are in the same boat.
My idea would be to reduce using a volumetric method. You can acquire an oral syringe from pretty much any pharmacy for free if you ask the Rph. This syringe will indicate volume by milliliters. So, you could crush up a pill, mix it into solution with 10ml water and voila, you have a system indicating each Ml of this syringe contains 10mg Quetiapine. From there, you could ingest say, 90mg on your first night, followed by 80mg the next. You could of course make a bigger solution and store it, but I much prefer the idea of just making this solution every time you need to dose.
Try this method out please and let us know what you think of it and how and if its working. Let us know if you have any questions.