i use a hard surface. Been doing it for years. it DOES NOT take much effort at all to close the gap. Just begin tapping it lightly and checking the gap. You'll see it doesn't take much to close them up a little bit.
However, I would go with the gap provided. If you aren't having plug blow-out at WOT, then there's no reason to close the gap. A smaller gap will reduce engine performance. it may go un noticed, but it will reduce the power.
Try the plugs as-is and only if you notice a skip at WOT then reduce the gap, but generally you want your gap as large as possible without blow-out.
Blow-out is when the spark cannot sustain the gap bridge with an arch and the engine basically blows it out from high revving situations.
Being that the Pulstar plugs are suppose to generate a much larger spark off the same voltage as a standard plug, .040" you'll be fine.