I just direct sowed them where I wanted them. Cover lightly with soil and then I put straw over them for mulch. Keep evenly moist. The ones I sowed this year just started blooming this week. They are really not fussy plants at all. If you oversaw, you would need to thin them out after germination. We have such a long growing season here, and I had fresh seed, so I just put in a seed only where I wanted a plant.

I sprinkle my zinnia bed daily until the seedlings emerge -- usually in 4 to 7 days.

I often make seed tape from (scarce) compostible toilet paper. I paste the seeds however many inches apart I want them, and bury the tape 1/4" or whatever the variety dictates. The paste I use is just flour and water mixed with a toothpick. Works great! The toilet paper helps keep the seeds damp, but it disintegrates quickly, and any roots go right through it.

Thanks for your ideas! I didn't see Cooper and Zen's comments until just now, sorry.