Use Script Editor to create a new AppleScript in ~/Library/Scripts/Folder Action Scripts/, I’d name it add – new item sync iPod.scpt. Script text is below.

Then right-click (control-click) on any folder in Finder, go to More, and then to Configure Folder Actions…

Make sure you check Enable Folder Actions, then click the + button under the Folder with Actions column.

Select a folder in the Podcasts folder (of your iTunes library), press Open.

Select the action, add – new item sync iPod, press Attach.

You should see something like this:

Script text:

(*
add - new item sync iPod

When a new item is added to the folder it triggers iTunes to do
an iPod sync.

Useful when you manually manage but want to be sure to have
fresh podcasts on your iPod. Unfortunately you have to setup
this folder action for each folder in the Podcast folder.
*)

on adding folder items to this_folder after receiving added_items
    try
        tell application "iTunes"
            repeat with s in sources
                if (kind of s is iPod) then update s
            end repeat
        end tell
    end try
end adding folder items to