Bearing repack practices

I am looking for some advice on bearing repacking.

I know that the best practice is not to open pillow block bearings in the field for grease repacking, as it just opens you up for more contamination. Fill and drain ports are a much better idea.

However I wanted to see if anyone else does this and what practices you utilize to reduce contamination.

Our applications are mostly horizontal pillow blocks on conveyors and fans at a mine site. Most of our conveyor bearings are pre mounted on the pulley shafts so we simply change the entire pulley assembly at once.