When disassembling LEGO sets, there are a couple of pieces that get really stuck together. I usually use the double Brick Separator. But when there is no space for them, I get a little bit of thread and slowly slide it in between the narrow space of the bricks. Then I just pull. Sometimes they are really stuck together, in that case I use the same technique except that I use multiple pieces of thread: first I slide in a really thin one, pull a bit, then I slide another one, and so on until I have something in that can’t just split apart.
For some reason, I usually have this issue with pieces 63361 and 11477. Once together, there is no easy way to split them apart.