I use a nylofume plastic bag as a pack liner. Others use a trash compactor bag.
Place bag in pack. Stuff quilt or sleeping bag in the bottom along with other items which I won’t need until camp or which I definitely want to stay dry.
Then gather the opening of the bag up and compress. Squeeze a bunch of air out. When it’s compact enough, twist the top of the bag to seal it up and stuff the “elephant trunk” down the front of the pack.
This and many other great tips can be found in Mike Clelland’s book, Ultralight Backpackin’ Tips. It’s definitely worth checking out.
Ultralight Backpackin' Tips: 153 Amazing & Inexpensive Tips For Extremely Lightweight Camping https://www.amazon.com/dp/0762763841/ref=cm_sw_r_cp_api_i_XRN-CbZC01PJ1
And so cheap too!
Skura’s 2nd edition gear guide - http://www.theoutdooradventure.net/2017/04/the-ultimate-hikers-gear-guide-2nd-edition-book-review/
Any of the fun, easy UL books by Mike Clelland -https://www.amazon.com/Ultralight-Backpackin-Tips-Inexpensive-Lightweight/dp/0762763841/ref=nodl_
This book will do you infinitely more good:
If you're new to lightweight backpacking, these books are a great place to start:
Swami's blog is also a fantastic resource:
This book heloed a friend who has hust finished the PCT this past year.