[Freesurfer] Surface-based normalization, smoothing and averaging

Dear Freesurfer experts,

I would like to have your help.

I have a volume data of a certain parameter on white/grey matter boundary (X.nii). What I want to do are as follows: Step 1: I want to register it onto a standard space using surface-based alignment and smooth it. Step 2: I want to generate the averaged images of several subjects on the standard inflated surface.

My questions are follows: Q1) For Step 1, I guess I need to convert the image using mri_vol2surf (X.nii --> X.mgh), then use mri_surf2surf and mris_smooth. If it is the case what should I use for <target subject name> for mri_sur2surf?

Q2) How to do Step 2?

Thanks in advance, Shige