Theres a technique that i love! its called autogenic drainage i don't do it exactly the way they taught me because i modified it to how i felt it worked best.
they way they taught me is you breath out as far as you can and breathe in only to fill about a quarter of your lungs, then breathe out as much as you can, breathe in a 1/4 breathe out again etc etc do that a couple of times, *key is try your hardest not to cough! you want the air to start to work its way down to those deep little tiny airways --i always have to curl my toes and squeeze something lol-- *
then you do a few normal breathes and by this time you should feel like you've moved some stuff from your lower lungs to your middle lungs i guess? if not go back and repeat the previous section.
Then after some normal breathes in adn out in and out, you take a sharp breathe in like a gasp. and breathe only 1/4 the way out then breathe in sharp like a gasp again, so doing the opposite of the first step and in turn it brings all the loosened mucus up to the top of your lungs and you'll be able to do one really good cough with a ton of gunk.
I find this sooooo helpful especially with some of those hard to get up crackles. But what i do is i just push out my air for as long as i can and then breathe back up and reapeat that trying to not cough. i don't do the gasp thing or the deep deep deep normal normal high high high cycle of the a.g.d system i just kinda do normal deeeeeep normal deeeeeeep normal etc etc and I find that it gets so much junk up.
it does take practice to find what really works well for you.