If you're applying the sealer by hand, go ahead and take five gallon pails, or if you're pouring out of one of your spraying systems, pour puddles of it, and literally squeegee and brush it back towards you, making sure you get an even coat. Don't leave a lot of excess sealer, because that's susceptible to drying out in the sun and cracking on that surface. So make sure to squeegee and rack properly.
We do advise though to spray with spray systems. You'll always have the best outcome.
Identifying whether or not you need one or two coats of sealer is really quite easy. If you need one coat, it's because the asphalt was just recently paved, or recently sealed, usually within a year or two. So then it would only need one coat.