Prior to retirement I managed a site that produced precision needle bearings. I preface my suggestion based on this fact.
Quality Assurance uses ultra-sonic baths to measure dirt particles. This was done by placing a container of mineral spirits in the ultra-sonic bath of water. Yes, the ultra-sonic bath contained plain water. For quality's sake, the mineral spirits was filtered and read for dirt count. For the sake of this discussion, you can do the same with your choice of cleaner in a can or jar placed in your ultra-sonic bath. Also, I have cleaned many disassembled motorcycle engines, some with caked oil, decades old. PB Blaster, WD-40, Mineral Spirits (NOT ODOR FREE TYPE), search paint thinners for real Mineral spirits. Dawn liquid dish detergent to rinse residual solvents. To remove silicon grease or anything with silicon use 50/50 acetone/isopropanol alcohol mixture. ALWAYS USE SAFETY GLASSES AND GLOVES. KEEP AWAY FROM SPARK & FLAME. NEVER USE CHEMICALS IN CLOSED ROOMS OR INDOORS. Sorry for the rant, but safety 1st. Thanks!