(One thing that seems for certain: explore isn't working like it used to - explorers get stuck and idle instead of actually performing actions)
First step: just make an incursion into enemy territory where there's a hostile wharf. I think any KHK station is the best choice here since they won't build capitals; if you set up by a xenon wharf, capitals will come in from elsewhere on occasion, and that will require micro. But you might consider it a cheat to target KHK based on, they have no economy.
Second: build a heavily fortified defense station say, 80 km from the enemy shipyard.
Next: buy yourself a large swarm of low-tier fighters, set their orders to "protect station". (I am using some heavy fighters and some scouts - scouts because I want small ship kills to count as hard if possible)
Here's what you get, an unending battle - your fighters won't go attack the enemy station, they just attack enemy ships that come near your station:
In vanilla, it still takes a while to reach 3 stars. You can mod experience gain if you want to. But, this approach seems at least somewhat efficient. Every time an enemy dies, every one of your ships that did damage gets full credit for an easy kill and partial credit for a hard kill.

Reference - viewtopic.php?f=181&t=424312#p4933124
Mackan explains how experience is divided between pilots who assisted on a kill.