Oh.. man.
The soil you're planning on using is fine. Don't dick around with flushing it (stop, think, flush? like water? yes! don't do it), just don't start adding fertilizers as soon as they've sprouted.
My predictor light went off, so here's a little pre-emptive information; if you're concerned with how to water seedlings then click on my sig and it'll take you to my gallery (the gallery link that we never got back
). Go back to the first page and you'll see how I handle the seedlings. They go in a tray, the water is put into the tray and I always keep about 1/2" or so of water in it at all times. Once they're mature enough for transplanting then they're treated like big girls and watered as one would a more mature plant. I lost one seedling using that method, and that was because it was blown off the deck and I couldn't find it.