I find giving the strop a good rub down with my hands before each use is enough, as the oils from your skin work into the leather.

Rubbing the strop before use also seems to increase the draw slightly and make the razor really sing over the leather

I'd only really use neatsfoot oil or the like if you're reconditioning an old strop where the leathers dried out some, or if you find that rubbing the strop with your hand alone isnt enough.

If you've got a new strop thats been made from decent leather you shouldnt have to condition it out of the box IMO.