I am sure many of you know this already, but am posting for the other primula lovers who might not.
Generally speaking, a very high percentage of primula species are easy, warm germinators.
In fact, very, very few require cold.
While germination can happen quite quickly with a few species (in the first 2 weeks, or less), the majority seem to sprout around the 3-5 week mark, with 4 weeks being the norm.
If you are in a hurry, or need/want to speed up the germination time and have the added benefit of higher rates (more consistency in germination), treat with GA-3 at sowing. Doing this generally produces very even across-the-board germination in the 10 day frame.
I have just recently sown about 75+ species and this morning (at about the 10-12 day mark) 90% are a sea of green.
When dealing with small seed like primula, I prefer to mix up a spray bottles' worth of GA-3 with water, surface sow the seed, and just spritz over the sowing.