Curious to find out how other email designers go about designing retina ready emails.

Currently, my set up is design the email within Photoshop and export slices for HTML build. However, considering making some key images in the email retina ready, so doubling the dimensions of them.

Would I be better off designing as I do, and then picking out the assets that I want to be retina ready. Or design the entire email as retina ready? But only save the slices that I want to be retina ready at those dimensions and reduce the size down of everything else?

Just thinking that I might have to change my design workflow for this!