Flattening a PDF using Assembler's Invoke DDX

I have an XDP that needs to be converted to a flat PDF without using output(The solution can only use forms services).

Since its being called from within the process orchestration by using the invoke DDX service, I'm totally lost as to how its done.

1. How do we select the input from within the properties tab without using the literal value ?

2. How do we set the required "<NoForms/> and "<NoXFA/>" parameters from within the workbench without using a literal value for the input parameter in properties ?

3. Would the invoke DDX service allow output to a OutputResult variable ?

Thanks,

Holy