A few yrs back (40+) I visited some cloud seeders out in MT/ID area. Their purpose was not to make it rain per se, but to seed the clouds with silver iodide (I think) to try &  make moisture fall rather than continuing to rise in very large buildups, often referred to as thunderheads. When the moisture droplets continued to rise, they froze & continued upwards, gaining size as they went up & made damaging hail to the wheat. The idea was to make the clouds precipitate before they started the huge updrafts. It wasn't unusual to find the planes with a lot of paint stripped off the leading edges. The seeders were just spray booms fastened under the wings fed from a tank in the aft area where rear seats normally reside. The cloud busters were hired by wheat districts by those that had paid in for hail control. This was all civilian stuff, no military.

Most of the planes we dealt with (bought them) were Piper Twin Commanches and Cessna Skymasters (push/pull). Nothing special other than most had installed thicker plexiglass to try to keep them from breaking out if they flew into more hail than expected. They also ran their own ground radar sites to watch the buildups. Not radar for air traffic, but radar for weather, though it would show planes within the area. I was in a valley in MT headed for an airport when some civilian guy came on the unicom frequency and told me there were 3 B-52s ahead of me in the valley. I asked how he knew this, and he said he was a cloud buster radar and had been tracking the B52s. When I told him I didn't see them, he said they were low...VERY low. They were.