Bicycle Mechanics - new derailer issue.

so, a few days ago, my rear der stopped being able to shift up to the two outermost cogs. I think it happened while I was messing with the barrel adjusters, trying to get the chain to stop slipping (this is all in a previous posting. thanks to everyone for the advice).
at first I assumed I went overborard with the fine tuning. but I just couldn't get it so that I could use the top two cogs. then I tried to set the high limit screw, but that didn't do the trick (and as someone pointed out, limit screws don't tend to unadjust).
now, fast forward to last night. the front derailer is acting up. it won't shift to the outermost ring, either.
the fact that it is happening both in the front and back seems maybe to rule out wear to the cables or housing, and to rule out limit screws (I think).
the obvious answer is to check for a bent der hanger or something. it's not noticably out of whack, but I can take it to a shop I where I used to work.
so, before I go to the shop, I'm wondering if there's an answer that pops out at anyone. I could be missing something obvious. I welcome any insight/advice/criticism. thanks you.

I think it is most likely in the cables - iether broken streands or dirt/rust limiting movement. Release the cables from the deraillers, and check that the cables can slide freely in their housings. While the cables are detached you can also check that the derailler cages can move over their whole ranges.

You need to eliminate the potential problems one by one. This is only possible if you have access to a repair stand or another way to get the bike up in the air. With the bike in the air, loosen the cable tension bolt/nut to take the cabel tension out of the picture. While pedaling, operate the derailers through their range of motion using your hand directly on the der. This will tell you if the stop screws are the problem or not. If not the stop screws then you now know that it is the cable tension. With this in mind you now need to retension the cables while the adjusting barrel is turned out about two full turns (in case you over tension you can back it off). Now try to run it through the gears. Adjust the cable tension so that your indexing system moves the chain one gear at a time. Check the shifting both up the sprockets and down because the cable needs to be tight enough to pull to the top of the sprockets but loose enough to let the chain drop on to the cogs on the way down. I lube the cables afterward unless that is obviously the problem in the first place because if you can make it work with out lube, it will just work smoother with lube.

This sounds like a lot, but once you start doing it this way you will eliminate all the questions one at a time. If it still does not work after that, then you know that it has to be something else (most likely) This is not whitch craft it is more like a math problem or a puzzle.

grok.