R – FlexBuilder to FDT Migration

I'm new to FDT and I'd like to move some (actionscript)projects from FlexBuilder to FDT.

I've noticed FDT can read .actionscriptProperties from FlexBuilder, so just setting the workspace to my FlexBuilder workspace got the projects, the current one open, the rest of them closed which is great.

I got a an error on the way:

"Error opening the editor.
No editor descriptor for id com.adobe.flexbuilder.editors.actionscript.ActionScriptEditor"

which makes sense…I the last editor used was the as editor from flexbuilder, which isn't present in fdt…no biggie here.

My problem is that I don't get the FDT autocomplete working, not even for the default AS3 classes( Sprite, TextField, etc. )

I've tried right clicking the project then Flash Project > Remove Flash Nature
then Flash Project > Add Flash Nature again…but it didn't seem to do anything.
I don't even know what it does. I'm guessing it's telling FDT to treat this project as CS3 or Flex compiled project.

I've also imported a project from SVN in FDT and no autocomplete.

So, how do I get the great FDT auto-completion for a FlexBuilder Actionscript Project opened in FDT ?