I am a hobbyist who started playing clarinet three years ago. I find voicing the clarion range in the bass clarinet to be a challenge, especially because I am a doubler who’s main instrument is the saxophone. So these two videos, starting from simple to slightly complex, are kind of helpful for me.
Of course this is all moot if your instrument is out of regulation. If you have leaks, you are so screwed. If your instrument is an old school beater, it can damaged with so many problems that you will never get it to play well. If you thought you saved money by getting a beat up instrument, you will have basically an unplayable instrument. How much money did you save then? I recommend you get the best instrument you can, even if it means saving up a little longer.
Of course, I assume that you do the long tone exercises to refine and develop your sound too. And we are not talking about sloppy fingering which can introduce a whole host of squeaking opportunities. This is just anti-squeaking 101. Good luck.