Everything you do to a reed is a compromise. A scraping operation will almost always give you the intended result, but it will also give a variety of unintended results which you must anticipate. Try to find the solution that solves the most problems and creates the fewest new ones. Try the reed after each operation. Don't decide you need to scrape the back, finish the tip and then clip it.
Results are sometimes unpredictable.
Do one thing at a time, and always try the reed. Learn to clip the tiniest amounts from the tip possible. If you can hardly see the remains on the block, it's about right. Consistency is more valuable than frequent experimentation. Try to find something that works and stick to it.