Damn, RC MK Hurricane Kicks are important in this match.
I think it’s better to play a defense/battery game with Sakura, and force him to attack you, especially if you can’t RC. Keep in mind that unless he is in N-Groove, he can’t break out of your custom if he blocks it. He can’t afford to let you gain meter safely. As a result, he’ll be on the offense, and you’ll be on the defense. If he refuses to attack you, whiff dive kicks until he changes his mind. From here, s.HK to push him away, j.MP/c.HP to anti-air, and if you can get him to block Hurricane Kicks, momentum is in your favor. Remember, he can’t afford to let you gain meter safely, so whiffing dive kicks and finding opportunities to make him block attacks are both dangerous to Blanka.
Once you have meter, it becomes a cat and mouse game, where your goal is to force him to block or get hit by the custom, and his goal is to get away from you. Don’t botch the custom, or else you’ll lose a huge advantage.