This was one of the first big problems I had to overcome. I was constantly coughing my brains out trying to clear it out but could not keep up. So, while I was in rehab, the RT got the doctor to put me on 1200mg extended release Mucinex twice daily. It has worked great since (for two years + now), and I don't worry much about it most of the time now. I get the Curist brand of it from Amazon Prime at literally half the price. I buy the 150 count bottle. Same stuff - Guaifenesin.
Interesting how different things work for some folks. I can only sleep on my stomach, as I cannot breathe lying on my back. I use a big pillow, and I also have an NIV machine (Non-Invasive Ventilator), which is like an advanced version of a Bi-Pap. I can't use it all night, but for periods of an hour or two. It helps expel the C02 from my lungs to allow more room for 02. Medicare provided it, along with the RT that comes with it. We need our sleep, and anything that helps that helps our health!