Lots of folks insist on pricey drying systems, but my regular box fan gets it done. The key is positioning it to move air across the whole panel, and I've had no problems with finish quality.
Right, @richard_perez makes a good point about dust from the floor. I mop the garage concrete right before I start to lock down that loose grit. Then I put the fan up high on a table so it blows across the paint job, not down at the floor. This moves air over the surface without kicking up all the debris below. It's all about keeping the air moving where you need it and keeping the floor as still as possible. The finish turns out fine because the paint dries even and dust doesn't get a chance to stick.
Ever worry about dust getting kicked up from the garage floor with that setup. A clean finish seems like it would depend heavily on having a really spotless area. How do you manage air flow without stirring up all the grit and debris.