There are no short cuts!
You will need lots of space, lots of time and lots of dedication.
"Pheno hunting" involves growing many plants of the same strain in the quest of finding that "one special" example.
This may not be readily obvious unless you grow between (at least) 20 and 50 plants of each strain.......preferably 100-200!
Some things to look for would include vigor, structure, nutrient efficiency, ease of cultivation, strength, leaf responsiveness, training resilience, flowering induction, flowering speed, flowering development, flower structure, trichome production, potency, overalll effect, disease resistance, pest resistance............the qualities to look for are only limited by your imagination.
It involves taking cuttings from each plant before the final outcomes are known, then persevering with only the cuttings from the most desirable mother plants.
Unless you are a serious grower with huge expectations and a defined goal to reach, the average home hobby grower is better off just growing random seeds as offered by the best breeders in the industry, who should have done this work for you already!