repotting questions

[novicej]

I have a few questions about repotting that I am unable to find answers. Hopefully some orchid experts could help me here. Thanks in advance!

So here are the Questions:
1. After cleaning up the old mix, no matter how careful I am, I always end up with a lot of broken roots with splitted velamens, a lot of time over half of them are broken (more so on ones with fine roots such as oncidium and less so on Phals or Cats). Now how should I deal with them? Should I bury them in new mix as is? Or remove the outer velamen and bury the "wires"? Or trim them (which means trimming a LOT of roots). Are the roots after the break point still meaningful?

2. Most repotting instructions tell you to repot when new roots are growing but less than half an inch long. However after my repotting the green tips on those new roots will turn brown (or white) in a couple of days and stop growing. Is this supposed to happen? I end up with a few very shot roots, although eventually a few newer roots will emerge from nothing.

3. For oncidiums I have a hard time leveling the whole thing because the older pseudobulbs grows new ones higher and higher. So I often end up with the bottom of the new pseudobulbs above the mix while half the old pesudobulbs are deep in the mix. Is that OK because I will end up with a lot of aerial roots for the new growth. What else can I do?

4. How to train new roots to grow into the mix? Or do I have to do that? Because it seems the barks on the top will block the roots from getting down and make them grow on top of the mix.

Thanks again! Any thoughts/discussions are welcome!