most air has yeast in it.if you are using molasses now then its already working.
as far as seeds.i saw traits the very next batch i hatched out.
say you made soil today then planted plants then let them go to seed.
then next year you start those new seeds,you will see some traits in them.
it happened last year with my pintos,and again this year with the alfalfa.i grow about five crops a year.so i see these markers very fast.
if you are about to harvest,throw some watermelon juice or apple juice on them a few weeks before harvest.you dont want your plants loaded with sugars at harvest.so water the last few weeks.no juice or nutes.but if you make a new soil batch,then throw in a bunch of seeds or sprouted dead seeds.sprouted and dead is better because ones that sprout in the soil will need to be pulled and thats just more work.
if you are around cactus,throw in some of them for water retention and root stimulator,its just aloe vera only of a different species.succulunts.
hope that helps