I find that if the spot-on is completely emptied when squirted directly onto the skin (by parting the fur in the correct area), there is very little run-off. The greasy fur effect is usually when more has landed on the fur instead of the skin. The greasy look should go within a day or so through grooming, although it's not ideal for cats to be ingesting the product. The smell will go in a day or so too.
Having said that, I find it quite difficult to part the short fur at the back of the neck whilst trying to control a wriggling cat with one hand - so I sometimes end up with cats with temporary greasy fur too
Advocate, Advantage and Stronghold are all very effective spot-on treatments so personally I wouldn't change them for that reason.
The instructions do say not to stroke them until the treatment has dried. Also cats should ideally be kept apart until the treament is dry in case they groom each other.
