Vintage, like regular ovens cast iron DOs vary between manufacturers. Everything from thickness of the iron to the type of iron formula and casting will factor into it.
Types of briquettes vary in temp output too. Most DO chefs find a charcoal they like and stick with that brand so they know what to expect. Like a large number of DO chefs I use the basic Kingsford.
If you have Lodge, start with the basic Lodge chart and just start cooking. There’s no teacher like experience. Remember that cooler weather and windy weather will affect the times and temps because you are outdoors instead of indoors. Humidity can als affect it. These aren’t like “set it and forget it” slow cookers. They need to be watched and smelled. That means staying close by to detect burning. If you think it’s burning remove coals and let the temp drop some. If it’s not cooking fast enough add coals.
It’s more an art form than an absolute science but I’m pretty sure most people can master if they’re willing to put their mind to it. It just takes practice. Here’s a copy of the Lodge chart to get you on your way. It gives approximates for the different size ovens.
Lodge Baking Temperature Chart.