This is a set built-ins I did two years ago. A full one third of the project was spent painting! I did it all with a brush and regret not getting a sprayer.
Probably not much of an issue in this case, since the TV isn't really central to this... But don't make the mistake I did in 2006 and build your cabinet to fit a specific TV.
A modern 65 incher will technically fit this 58" TV-shaped opening, but it'll be a combo of awkward narrow & wide gaps.