It’s simple, SHIFT-3, paint some foliage, SHIFT-1, save your level.
You can paint rocks, and then paint some grass the next day, and paint some trees a month later, doesn’t matter.
These are normal meshes you’re painting, they don’t need to be special meshes. You might be getting confused with ‘foliage-type’, which is just a browser item which contains a record of which mesh and which settings you used.
When you paint foliage, all the meshes placed are ‘instanced actors’. That means that, the moment your brush hits the deck, Unreal makes one actual mesh ( which you never get to see ), and all the others are actually just copies of that one mesh. When you run, the graphics card only has to draw one mesh, all the others are just hardware transforms of that single mesh.
Having said all that, painting foliage is a ‘whole thing’. The fewer polygons in the mesh, the better. The quicker the mesh LODs, the better. The less you paint, the better. It’s a bit of an art form.
