Firefox UI interaction

I’m trying to automate transfer from one data system to another web based system that will not work with safari. I’'ve tried using UI Element Inspector and UI Browser but neither of those can target the text fields I want to enter data in. I’ve been trying the DOM Inspector in Firefox, but that doesn’t seem immediatley helpful for what I’m trying.
Really, I just need to enter data into fields in Firefox through applescript. Can anyone give me a hand?

Search for some of jj’s solutions for this. I’ve seen several.