The most idiot-proof ftp interface I've found is Dropbox, especially when using it locally, through the OS; treat the Dropbox folders as local folders, drag and drop files into said folders, share public links with a right click on the files/folders you want to share, paste it into an email.
It's a little more complex when sharing private folders, but even then it's far easier than most ftp software/browser interfaces.
The most idiot-proof ftp interface I've found is Dropbox, especially when using it locally, through the OS; treat the Dropbox folders as local folders, drag and drop files into said folders, share public links with a right click on the files/folders you want to share, paste it into an email.
It's a little more complex when sharing private folders, but even then it's far easier than most ftp software/browser interfaces.