Sometimes I need a bulkhead fitting on a barrel or IBC and don't have easy access, or arms long enough. When I was putting in a potable water tank on a bus I learned about spin welding fittings on plastic tanks. You have a plastic fitting that you spin against the tank and it melts/welds itself to the tank for a leak proof seal. The fittings cost are often less than a bulkhead fitting.
They come in all sizes male and female. The tools to spin the fittings are incredibly expensive, but it isn't something that a handy person can't make.
https://www.youtube.com/watch?v=fMdLWAYr7Ck