Thankfully we have a lot of ways to put counters on our creatures during our main phases to trigger this uncommon
Open The Armory Open The Armory is one of the best tutors for Voltron decks
Whatever way you decide to use Tergrid, the card is powerful and will require a silver tongue to politic your way into keeping it around
Drop Valley Rotcaller with a haste enabler like Swiftfoot Boots and an army of squirrels, and youre set
You could also consider Stonjourner (121) from this set as an option, as it is another Basic Pokmon, has a solid 130 HP but also has a strong Ability, Exoskeleton , which reduces the damage it takes by 20 from attacks (including your own, though thats not relevant here)
This doesn't guarantee you a gold/crown card, but it does increase the chances of it giving you a gold card to 3.846%