Sleazy Fork is available in English.
Can work on almost any webcomic/manga page, preloads 5 or more pages ahead (or behind), navigates via ajax for instant-page-change, lets you use the keyboard, remembers your progress, and it's relatively easy to add new sites
Can confirm to not be working on raw.senmanga.com galleries. It works on regular senmanga though.
Senmanga is not working
Senmanga is not working anymore. Please fix it. Thanks in advance.