I would spray them with cellulose (or similar) using a HVLP turbine and gun.
Cellulose is a "hot" paint, by that I mean if someone has previously used "bog standard" paint, the cellulose may interact with the previous paint. A quick test is to lightly sand a section and apply some cellulose thinners with a rag and see what happens. If nothing, you are good to go. If it does re-act, you need to spray a special primer first.
The paint stinks but will dry/cure much faster than either water based or oil based paints. Touch dry will be very fast, full cure will be about 12 hours. Full cure for waterbased paints is about 3 days, weeks for oil based. Exterior 2K paints cure even faster because you mix a catalyst with the paint but they require specialist breathing equipment. When using 2K on a warm day, touch dry/lift up time is about 20 minutes, and I can sand it after about an hour
If you use a brush and roller, you are likely to either clog the holes or find paint dripping down on the inner face (and possibly the outer face as well).
If you are not bothered about the quality of finish then I would recommend an oil based undercoat and oil based top coat (you can add terebene to speed up drying). You can get grey undercoat if you go to a proper decorators' merchant.
