I have a Shimano Deore XT derailleur, with Shimano Deore LX shifters. Everything was working fine but the shifting got a little messy so I did everything according to the park tool's tutorial on derailleur adjustment. I adjusted the high screw, the low, then the B screw (I don't really get the B screw because there is a large range of settings for it that seem to all work), then adjusted the barrel on the shifter just like they said to do.

Every time I do this, it's easy to get a nice shift inward (to the biggest cog), but then you shift back outwards and the chain never wants to go back down. So I'm left with the option of adjusting the barrel screw, I guess? I make it looser, but then I have problems going back outward the other way when I shift because the barrel screw is looser now.

It's like only one or the other works, and I've done this whole process literally 20 times, trying all sorts of variations of adjustment, but I can't get this to work. I am pretty sure my derailleur isn't bent, it looks ok, and my chain isn't that old. I am ready to give it to the shop because I have no idea why this isn't working but figured I'd ask to see if anyone knows any tricks.

Thanks!!!!!!!!!!!!!