Can I paint oil base primer in direct sun? I have heard you should not paint oil base paints in direct sun.
Yes you can. You simply need to condition the oil base paint so it doesn't set-up too fast and remains workable. A splash of paint thinner can be used or a paint conditioner for oil base paint and primers, Penitrol is an old staple for conditioning oil base paints.
As you work the paint will get thick, you might have to add a little extra thinner or conditioner.