Starting Marigolds from seed

I've always started my Marigolds from seed
Usually I harvest the dead flowers (seeds) from the year before & plant them the next year
One year I had about 130 Marigold plants that I grew out back & then transplanted to the front

I also collect seed from other marigolds at friends houses

I'm not sure where Pgh is
I haven't planted any outside yet
I have started some inside

Usually outside I just sprinkle them on the ground & cover with a very light sprinkle of dirt
After they sprout I spread them out or transplant to another area