You declare attack with Jumbo Cactuar, and then once it gains +9999 attack, you cast Swords to Plowshares on it
The latter is true of Hour of Promise, which gives you a few blockers and ramps into any lands you need, not just basics
That said, considering it has to be against a creature and not simply target, means you wont be getting the benefit from hitting players themselves, or opponents can simply choose not to block with one of their creatures and that means no counters, but with spells like Duel for Dominance or Ents Fury that forces Wolverine to attack an opponents creature or enchantments like Fire Whip can mitigate this restriction pretty easily
Nobody wants to spend their mana to remove your 0/1 flier thats just sitting there, right
Monster Manual costs four mana up front, but you then can pay two mana and tap it to put any Creature from your hand into play