All you have to do is cast spells on your opponents turns, which is what high-level Commander decks want to be doing anyway
Beyeen Veil / Beyeen Coast Beyeen Veil is a nice trick for Limited and thats all
Play Boosters are widely considered the best all-around option in Magic right now, especially if you enjoy Limited formats or want flexibility when building decks
Sonic Screwdriver, Psychic Paper, and Rogue's Passage are all ways to accomplish this so your game-enders like Rose Tyler can swing for lethal damage at your opponents
Don't underestimate the ability to buff your opponents creatures when they need it though
Commander, which is reminiscent of a former game format called Elder Dragon Highlander, or EDH, is a format where players build a 100 card singleton deck, built from the card colors contained within the color identity of the commander of the deck, which must be a legendary creature or one of the special Commander planeswalkers created by Wizards of the Coast