For right now I have a camera that ML can't be used on. I was wondering, what can I do to replicate Dual ISO? Is there a way, or must it be done when the picture is taken?
Dual ISO is done by alternating exposure between sensor lines. So it can only happen when the picture is taken.
You can, though, do HDR images with any camera. I recommend HDRMerge (http://jcelaya.github.io/hdrmerge/).