The way I’d do it is by using text item delimiters, these provide a fast way of dividing a string to make a list. Like this
set aString to "2,69,12"
set {myTID, AppleScript's text item delimiters} to {AppleScript's text item delimiters, {","}}
set myList to text items of aString -- Gives list {"2", "69", "12"}
set AppleScript's text item delimiters to myTID -- It's considered good practice to return the TID's to their original state
repeat with myItem in myList -- Loop through the items in the list
--Do your method call here
end repeat