The general idea behind Montage is to get a big 9K+ beat stick out from using Yubel (s). There isn't another card that works like that available right now.
use fire king island or the fire king monster to destoy yubel in hand, then ss the 2. yubel, and sit on that until you can summon montage dragon by discarding the rest of the yubels and the attack with the gravekeeper.
easy peasy, and the ai wont use the board wipe since it does not find yubel as a threat.
Yubel is to hold the line while you wait for Montage. I usually find Montage is near the bottom of my deck, in the mean time you just have to keep thinning out your deck.
You can use the calculator and 2 union on vassal for the same thing, as long as you have a yubel on field too. Attack won't be as high, but with 2 union it will do
Calculator is normal summon, maybe u need at least 1 double summon. Be carefull if he activate his field spell, it will cause effect of yubel (1) miss timing when your yaksha is destroyed by battle