Heya...
Read the sticky again- that mix is too hot for seedlings; try an unfertilized seedling mix or even promix.
Also, you need to plant BEFORE the leaves show! Like, the moment you see enough tap root to figure out which end goes down. And don't water much. LIGHTLY.
Definitely practice on bagseeds. Ask TRUSTED friends to save them for you (they may guess you are growing so be careful who you ask) if the bags you get have hard-to-sprout seeds.