According to Mr Schewe (sharpener guru), in the current LuLa video tutorials, if the native resolution of your image will print under 360 PPI for Epson or 300 PPI for Canon and HP, upsample to 360/300 in LR and apply the correct output sharpening. If the PPI is over 360/300 but below 720/600 PPI, upsample to 720/600. Put the Dimensions check box on in the Print module after you select a template to see the values discussed.
When I tested this using a very high frequency image with lots of detail, I did see a slight improvement as Jeff suggests, but you need a loupe and keen eyes to see it. This was on an Epson 3880.