I almost never start from seed honestly. And when I do I ALWAYS use rapid rooters. I don't sprout them first either, I just soak the seeds for about 12-16hrs in water then stick them in the rooter about 1/4" deep. But as BudGoodman mentioned with rooters you don't even need to presoak the seeds. I just do it out of habit.
If you're having trouble getting the seeds to root out fully, it could be your starters are too wet. Which is common with rockwool. Next time before planting the seed, give the wool starters a bit of a shake or place them on paper towels to remove some excess water.
I had this idea to remove the excess water from the Rockwool cubes after prepping and soaking them, what do you guys think?
1: Fully saturate all cubes with properly mixed starting solution
2: Stack the cubes one on top of another
(It naturally starts draining excess water from the top cube)
3: When the top cube feels properly drained move it to the transplanting area for the next stage
(I compared the weight to well shaken out cubes)
*Wait to transplant until every cube is properly drained!!
4: After the first half of the cubes are at the proper moisture level; repeat same process stacking cubes with the bottom row
5: Repeat steps 1-4 until you have one final soaked cube
6: Shake out your last cube, you are done!
(Time for transplanting)
I came up with this after shaking out 33 4” cubes, definitely saved my arms which were beat the whole next day anyway