A bit more info those who have not used ACM panels. I would guess that most people who paint on ACM / Dibond, don't paint directly on the polyester coil coated primer that comes on the panels. I always add some sort of primer / ground on top of them after wet sanding with 400 grit paper but not breaking through the factory primer. I use XIM UMA as the first coat, then different surfaces on top of that such as Gesso, Oil Ground, Acrylic Medium etc. The white primed panels as you noted, are extremely slippery, but they are designed to be painted or printed on by sign makers, so it should be OK to paint directly on it, particularly if it has been roughened. Some artists also paint on anodized aluminum.
Some day I am going to try some "liquid sandpaper" on an ACM Panel, which is essentially a chemical that roughens up the surface so that new layers will adhere better. I would imagine that the same chemical would work on those slick Ampersand panels. Once finished doing the job it is removed with nothing left on the surface so you would not need to worry about it interacting with your paints in a negative way.
Originally Posted by Richard P
I've not painted on an oil primed surface, but dibond is very smooth and hard to get good coverage on in one layer.
Richard, you might want to try an oil ground on some Dibond / ACM. You can use regular white oil paint to see if you like it. I prefer a mix of lead and titanium white oils plus a bit of alkyd medium to speed up the drying and to help it self level. If it is too slippery for you, you can add a bit of calcium carbonate / whiting / chalk / marble dust to it. If you add a lot of grit it will end up more like acrylic gesso.