+1 to Ericachristina. I could never fit all dat hair in the sink. I tried rinsing upside down once in the shower but my hair got way too tangled. It's just a hot mess. Nobody's fault but its own. Ignore it please.
& try rinsing upside down if it's worked for others! But if not, just do what works for you. I also get very annoyed when I try something that's tried and true for others but fails me. But ah well. You've got to do what works for you.