Filling in larger holes

Ok today i made a little more room for the water door and drilled the holes to secure the city water connection.
I was wondering after I CPES and paint Charley, and start putting fenders, front marker lights and water connections what would work well in sealing these holes. Was thinking that spray foam that is used to seal windows and doors in homes. What did you use? Also did you chaulk around these fixtures? Thanks