[logfromblammo]

Lower a vertical baffle grid into the hold with a crane. Secure it to the hull. Fill the hold with bulk cargo. Ship it. Raise the baffle grid with a crane. Unload the bulk cargo. Repeat from start.

You just need open tops and open bottoms in the grid. Open at the top so the cargo can fill the cells between baffles, and open at the bottom so the grid can be raised out of the cargo.

[astrodust]

You'd probably have to vibrate the cargo and/or the baffle to get it to settle in, which could be tricky, but it's not impossible. Not a bad approach.

[mcguire]

The hatch would need to be the same size as the hold, as well.

[logfromblammo]

The baffle grid would need to be the same size as the deck opening. Those are rather large on bulkers, AFAIK. Permanent baffles with open sides can be installed in the sides of the holds. I think those parts probably have sloped sides to follow the bowl shaped cross-section of the ship anyway.