Here are my tools for lighting. I like this MAPP torch, as I can aim it precisely at the spot I want to light, but from a safer distance (see earlier post in this thread about sparks.)
https://smile.amazon.com/gp/product/B00008ZA0F
And the FiAir is handy if you don't have electrical power nearby for the hairdryer option.
https://smile.amazon.com/gp/product/B00D5FS7HA
As for "why not light from the bottom?" - my ass is getting too old to get down on my hands and knees to light the grill from below, plus it's hard to see what you're going. And, removing the lower vent door every time you light the grill will eventually loosen the snug fit that holds it in place.