FIREFOX_PROFILE_DIR=~/.profile1 firefox FIREFOX_PROFILE_DIR=~/.profile2 firefox
firefox --no-remote -ProfileManager
I do wish -ProfileManager implied --no-remote though -- I wonder whether there's a reason it doesn't?.
EDIT: I just found `firefox -P` elsewhere in the thread. Also it seems like -ProfileManager does imply --no-remote now. Yay!
[0]: Or a shell script in my case, but a shortcut is probably more "accessible".
firefox --no-remote --profile /path/to/profile/directory