I personally have been using FCG http://www.dehats.com/drupal/?q=node/7
for a long time. It's an AIR app and it works good. Downside is that it is outside of Flash Builder UI but it's still faster than hand coding.
Right now I'm reading the article http://help.adobe.com/en_US/flashbuilder/using/WS52085436-ABD3-4d4d-B5E2-41C668CF6847.html#WSB1113812-F57E-4e7e-A64D-D6D34EF08B07
and trying to set up actual template files in Flash Builder guided especially by the comments at the bottom of the page.