x2 on putting silicone on your "never use" list.
For holes where cables and pipes go thru, I fill them up with polyurethane foam sold as "Great stuff" ... it is really great in sealing, but can be messy, so use precaution and practice on your shed before RV.
Than for final caulking use real roofers caulk or I like siding caulk from James Hardie that can be special order in colors from Home Depot. It has to be SO in 12-pack, but price was low last time I bought it.