My process has always been to clean up my file storage to my PC. I connect my phone to the PC probably 2-3 times a week, select which files to copy or which files to move off my phone. This does double duty...keeps my phone somewhat clean AND more importantly...makes sure I have a complete backup of everything!! Last night it came in handy, when I borked the phone, and had to reroot, super wipe and redo everything, I had all my files backed up to my PC...just ran Wugs again, copied all my files back and reinstalled my ROM. However, you can manually clean them up through a file explorer, like ES file explorer or through ROM Manager as well. Good Luck!