Theres not that many ways to generate tokens with prowess, but there ARE mechanics like Heroic or Jeskai Ascendancy which can simulate your team all having prowess very easily and keep that all-important efficiency high
4 Mutant Menace Spread Those Counters The Mutant Menace deck is designed around the commander, The Wise Mothman, a mutant who distributes Rad counters to all players when he attacks or comes into play
It dries faster and doesn't smudge as easily
Timetwister If you look through the list of mechanics in the games history, you occasionally see effects like Timetwister
Team her up with legends like Anje, Maid of Dishonor or Vito, Thorn of the Dusk Rose, and suddenly your reanimated vampires refuse to leave the party
This ability is usually found in white and usually only targets creatures