I am singing on these videos (sorry). Yes, I know that I am not a singer. I did save you from listening to me sing the 9's song. :) It is to the Star Spangled Banner, so I just posted the numbers.
When using these songs, have the students hold up one finger each time they sing a number. That should show them that the number that they are skip counting by times the number of fingers that they are holding up is equal to the number that they are singing. I hope that these songs are helpful.