Updating Flexitask custom fields

Hi guys,

I'm wondering how to update additional fields in the Flexi-task content type.

I create a assign flexi task action, and can set the Title, but I would like to set a few more additional custom fields so that elsewhere on the site I can use a content query to filter the tasks assigned to me.

Don't seem to have much luck -  the assign flexi task action waits while the task is pending, I tried using parallel process with the task ID but that didn't seem to work either.

Any tips?