A one-word answer: none!
When you’re painting your siding and trim, don’t skimp on the paint. One of the biggest problems do-it-yourselfers make is overthinning the paint or not applying enough.
So avoid the temptation to stretch your paint supply by adding paint thinner. You need thick coats of paint on your home’s exterior.
Also: Choose a full-coverage paint, especially if you have a home up north. On wood siding, semi-transparent finishes don’t hold up well. The higher up your house, home, cabin or castle sits, the harder the sun’s ultraviolet rays will attack the wood. You might get away with using a semi-transparent stain on your Phoenix home, but it won’t last five years on your mountain place, especially on the south and west sides of the home.