No need for a real blast. Just unzip and release them. Orbital dynamics will spread them out. Combinations of sunlight, magnetic fields, jostling with each other will spread them out over a period of days.

They might do like SpaceX does with Starlink. Rotate the vehicle slowly and then just please the payload. A very slow spin will impart enough delta-V to cause them to slowly spread out.

Station keeping tries to keep these satellites within 0.15 degree of their slot. That's about 60 miles worst case. Releasing a few million ball bearings could be awful, especially since you get "another shot" at a collision with any specific satellite every 12 hours.

There have been two confirm hits by space debris on geostationary satellites already with another 20 suspected. That was because of accidents. Now imagine several tons of debris specifically put there for that exact purpose.