I currently use Dropbox to transfer client files, or I will use Google Drive upon request. Dropbox transfers may be provided as a Dropbox share or a download link.
Download links can be easily shared by the client with family and friends for a limited time. Shared Dropbox folders do require that the client have a Dropbox account. Likewise, Google Drive shares work best if the client has a Google account.
I primarily provide electronic files to the client after a session. I can recommend possible print services if the client would like prints of their files. However, I do offer print services upon request.