For this build, it's going to be Guiding Zombie. He's the Granblue unit that you can call out as a Rear Guard when you ride a Grade 1 Vanguard. His effect also is when you add him to your Soul from the Rear Guard position, you can mill the top 3 cards of your Deck.
The basic strategy is Superior Riding into a Grade 3 as a starting point for the Vanguard. So, let me point out the materials needed for Superior Riding:
Please note that you can use ANY Grade 2 Vanguard, not just strictly for Grand Blue. With this though, there's another strategy.
Alternative Strategy "Resurrection":
The alternative strategy is "Resurrection", with such cards listed below:
With such cards "resurrecting", you can have both Rear Guard attacks at 20k, constantly. Which causes your opponent to use 10k Shield and a 5k Shield, or 3 5k Shields at one sitting, which depletes their hands of Shields quickly, and cleanly.
With 16 Grade 0 Shields (10000) and 10 Grade 1 Shields (5000), you would have plenty of Shields to guard with for a duration. With Skeleton Swordsman as an interceptor, it becomes a 10k Shield, otherwise it's a 5k Shield. Also, the other Grade 2s are 5k, regardless if they intercept or they come from hand. If you use Gust Jin, you can block an attack completely if you discard a card.
Be careful when you mill a lot, because if you mill too much, and your deck goes to 0 cards, you lose the Cardfight. It's the one thing you need to watch for, in addition to, watching your damage, so it doesn't hit 6.
Sample Deck List:
4x Gust Jin
2x Evil Shade
4x Ruin Shade
If you guys have a question, leave a comment.