I didn't post this in the rulings/bugs forum, because I'm pretty sure I've just forgotten how to you do this.
Basically, certain cards like, Bujin Yamato, have optional trigger effects that activate during the End Phase of a turn.
Effect Veiler negates the effect of a monster, until the End Phase, which is a mandatory lingering effect.
According to the breakdown of the End Phase (as we know it), when both players declare they have not intention of resolving/activating a card, or effect, at that point they MUST activate/resolve any mandatory effects.
Once this has occurred, the game state becomes "open" again, meaning the turn player, and then the opponent can choose to activate further cards, or effects, or proceed to the End of the Turn.
So the problem, I can't remember how to "wait" until Effect Veiler resolves to activate an effect like Bujin Yamato on YGOPro.