Buddy just had his whole house done, painter told him to hit it with water through a pump garden sprayer, stuff fell off, painter came in and did the rest
I'd make sure no waterproofing needs to be done on the outside of the foundation before worrying too much about underneath the house. You may need some french drains in some problem areas, etc. If you are confident none is getting in, then a vapor barrier may suffice.
I thought vapor barriers...