Absolutely do not try the wax thing. It will ruin your new paint job! You'll only end up with problems using wax over a satin, semi and especially flat finishes. The wax will get stuck in the slight (microscopic) porous surface and turn hazy white the first time it gets wet and then dries again. Then it will be trapped there and cause problems if you try to paint over it someday and don't get it all off.
If this is going to be a complete new paint job the absolute best way, but also most expensive to get a durable flat UV resistant finish would to use a urethane basecoat and topcoat it with either pre-flattened 2K urethane clear or you take regular 2K gloss clear and add flattening agent until you get the gloss desired, usually 40% by volume will yield a satin finish. For semi-gloss you'll want to be more in the 30-35% range ( do a test panel to get the ratio you want ) Never apply regular wax to anything other than a gloss finish, it will cause nothing bet problems down the road. There is a company in Europe that makes a special wax for satin finishes but its about $180 a can or you can get their whole satin paint care kit for $1800
PPG's Omni line is a very good and reasonable priced urethane basecoat and USC makes a very good inexpensive clear, that is only about $60 for a gallon with a qt. of activator. I believe Dupont still makes flattener in qts. I have also used PPG's pre-flattened clear but it's a bit more pricey. Most likely you can find a much cheaper line if you go the pre-flattened route.