With Designer 2.1 and 2.2 you no longer really have to pre-generate forms .. if you know you want to use your customized templates (and we have included in-line form editing for task forms) you can create a process form by clicking on the human icon in the top-left corner of your canvas and you can create individual task forms by clicking on the human icon on each user tasks shape menu (which shows up when you select a user task node). You can of course still pre-generate the forms and then edit them inline as well to suite your needs (see video here for more info: http://surdilovic.wordpress.com/2012/04/10/jbpm-designer-version-2-1-released/).
HTH