Rinsing undercarriage after Woolwax

Finally got around to lifting up the truck and protecting the undercarriage. Used Woolwax which went on surprisingly well. The coating was thick and self leveling. Drove it on the beach and decided to rinse because some sand had collected in the expected areas. The result was the coating to be not eased off but puckered by the stream of water( it was a light rinse) and the sand was still adherent in the end. Should this be concerning that grime is imbedded in this and when I go to coat next year, how should I clean the truck beforehand. Thoughts?

 

The more grime, the merrier is how I like my undercoating. Cant stop woolwax/fluid film from picking up dirt as it never dries. Just spray another coat on top next year and dont worry about it.