Got called out to a large Bar & Grill yesterday. No grease trap & a 160' run of 4" cast. Line was full of soft/tar like grease. Rodded through it 3 times with a doulble bladed 3" grease cutter and twice using a large spring retriever with my Spartan 300 with .55 cable. The first time I brought back about 20 mice. This line wasn't opening. Hooked up a flush bag and line opened right up. I then rodded through it two more times running a lot of water.
What would be the preferred blades and technique to properly open this gummy line using a drum machine ?