Hi, I'm new to creative sharpening and have a couple of questions.
1. Should creative sharpening be done on the full resolution image or the final output size.
Yes...after capture sharpening (in either ACR/LR or PKS 2 but not both) creative sharpening, which should prolly be done locally rather than globally, should be at the native resolution of the image you want to keep as your hero image. Whether or not you keep all the individual layers is up to you-I tend to and accept the larger file size. But...you want to apply creative sharpening carefully. You really should apply and evaluate creative sharpening at the screen zoom of 100% (one image pixel for each screen pixel) because display sizes lower then 100% applies display dithering that make the Photoshop display less accurate.
2. What would be the recommended sharpening effect for sharpening details in portraits such as the eyes.
Sorry, too broad a question. It all depends on the source of the image, the ISO the quality of the lens, etc. What I can tell you is a little creative sharpening for lips & eyes (there are lots of types in PKS 2-try narrow edges 1, 2 or 3) plus a separate application of smoothing for the skin will help. For skin smoothing, try Detail Subtractor in smoothing effects and/or Negative Midtone Contrast (like a minus Clarity in ACR/LR) in special effects.
Lots of things to play with and try...