Problems populating and submitting form/clicking button in Javascript

I usually solve these with trial and error but I am not getting anywhere with this one. I want to click the Subscribe button in Google Reader, populate the form, and then submit it or click the add button.

I am not sure if the form needs to be expanded before a value is populated. If it does, I need help doing it.

Once it is expanded, this will populate it

tell application "Safari"
do JavaScript "document.getElementById('quickadd').value=''" in document 1
end tell

Lastly, I am not submitting the form properly.

do JavaScript "document.getElementById('quick-add-form').submit()" in document 1

does not add the rss to my subscription.