Everytime i wet clean it takes ages. The first few passes always makes it much much worse but about 2 hours, half a bottle of eclipse an entire packet of pecpads later i can usually get it down to "only a few blobs at f/22".
I'll admit its a process i dead doing and my 550D and 70D need it every few months.
I believe you are "hitting the wall" or the "point of diminishing returns". It should not be a "marathon" or even that difficult. If you can't see improvement after 3 or 4 swabbings, then it's best to just leave things as they are and come back and try again the next day.
There are several "dry" tools that may help you out such as a good static-brush, SensorKlear pen or gel stick. This would allow you to concentrate your wet tools on the middle of the sensor, staying away from the sidewalls by about 1mm or 2mm. Then you can use one of the dry tools to go right around the perimeter.
Most people see their bottle of Eclipse last for many years, so I'm not sure where all of that fluid is going. Is there a possibility you're using too much per swabbing?