The biggest difference between violin/viola bow grip and cello/bass bow (French bow, not German, that’s a whole different technique of bass bow playing) is that the latter is more about power. You want to allow the weight to basically flow from your upper back down your arm, wrist, and hand into the bow.
As an exercise, try this… let your hand dangle from the wrist, loosely. See how the fingers hang? Next, lay the cello bow against the fingers – it should only be touching the bottom 2 phalanges (the ends of your fingers). DON’T squeeze it! See if you can see the inside of your first finger joints between the wood and the hair. Next, curl your thumb up JUST ENOUGH to press the wood stick against your middle finger, like you’re pinching the bow between thumb and middle finger. Just the corner of your thumbnail at the corner where your frog meets the stick. All 4 fingers should be over the stick so the weight of your arm and hand is over the bow.
We cellists sink down into the strings rather than pull down like a violin bow. In fact, it’s actually rolled the other way – on violin/viola, the bow hair should be closer to you; on cello, the wood stick should be closer to you.
Things4Strings sells a bow grip aid called a Cellophant that helps guide your hand into the proper grip. See: