You could spray the ones you see with 3% peroxide cut 50/50 with water . You can get Gnatrol at most home improvement stores and dissolve it and water in for the rest . They're not hard to kill .
I grew 3 different strains from seeds found in dispensary weed one year a ways back . All were found in weed labeled "2nd" cut . They were all female and they were all very good smoke . They went directly in the ground , no pots .
Garden Tone outdoors since the early 80's . We used to buy bulk blood meal , bone meal , dry chicken manure , and green sand and mix up large batches . One year all the blood meal was rancid and out of necessity we used Espoma . Never went back .
Dude I'm not trying to be a dick but you're in for a disappointment . Your plan is not feasible in any way . But you do you and be sure to let us know how it goes .
To put it very simply , in most cases you would go to flowering schedule when a plant has vegged to 1/3 to 1/2 the size you want it to be at maturity . Most strains I've grown will double in size during flower , some triple , and a few sativas even more .
How long that takes is dependent on...