EDITING + WORKFLOW: I use PS for all skin retouching. What is the best workflow for using VSCO Film?

VSCO Film only really works properly on RAW files so you can't edit in photoshop first without converting to RAW first in someway. Although we know that smoothing out some of the grain from an image after VSCO Film has been applied can have a very unwanted result.

Here's the work around to this: 
Apply the "Grain - None" toolkit preset to all the photos before you export from Lightroom, or just turn grain off and copy/paste the settings to all your photos. Now do all your processing in PS as normal and re-import the finished files back into Lightroom. Apply the preset of the grain you want (it'll look crazy, don't worry) and select "copy settings" from the settings menu. No uncheck everything except grain in the window that follows. Hit ok and now hit the "Reset" button at the bottom right of Lightroom. Now, go to library mode, select all your photos and select "Paste Settings" from the settings menu. This will just apply the grain settings to all the photos now.

If you'll be doing this a lot, you might want to just create a few presets for the grain you typically do. To do this, get it set how you want on a photo, then hit the "+" button up near presets and uncheck everything except Grain and call it whatever you like. Now, in the future you can just apply this preset to files you bring back in to Lightroom and save some time. It could also be helpful to create a temporary Lightroom library just for importing/exporting photos with grain, that way you don't have lots of extra files in your main library.

Lastly, if you have our ACR version of VSCO Film, you could also open all your processed photos in Bridge, select them all, right click and choose "Open in Camera RAW". From here you could do the same kind of thing I just walked you through and then save the images from right there, avoiding the whole import/export into Lightroom thing somewhat.