I used bettertouchtool. Where I can define keys global or specific to an application. When I first switched to Mac, I kept using Windows shortcuts in Chrome, so I recreated a large set of them this way. And, then Firefox. I even have some Ctrl shortcuts for Safari, even though I never used Safari elsewhere... Just muscle memory that Ctrl-F is find rather than Cmd-F...
The only thing I haven't gotten working using BTT is some way to shortcut "Open Link in New Tab" that get's around sites that hijack such attempts, etc.
The Dreamer