I'm strongly suspicious of WC being the one who did the actual act of murder. There's just way too many things that have a direct or indirect connection with her.
I'm likewise strongly suspicious that JF was an accomplice after-the-fact, i.e., he helped WC clean up the murder scene (WC's home) and dispose of MC's body. JF's life and financial situation is so intertwined with and dependent upon WC that he probably believed it was worth it to help WC. Also, I do not buy into the notion that MC would meet or go any where alone with JF.
I suspect the R Bros were "paid" by JF to ditch MC's car in PC. JF was familiar with the R Bros (ex-employees), he knew of their dislike and distrust of LE, he knew of their lengthy criminal records, he believed they could be trusted to perform such a task without saying anything to LE about it, and he knew they would be desperate enough to fund their Meth addictions that they would likely agree to it.
While the R Bros ditched MC's care, WC and JF cleaned up WC's house and then transported MC's body to the Spec house for temporary storage.
I believe the R Bros' role was solely limited to ditching MC's car. They, however, made one mistake: they left fingerprints on or in MC's car. LE was able to quickly match their fingerprints to those on/in MC's car because they are felons who were convicted of several felonies in Chelan County, which means the records regarding their fingerprints could be easily and quickly accessed by local LE and compared with the ones found on/in MC's car.
After matching their fingerprints, it took 5 to 7 days for LE to physically locate the R Bros. On the same day, the R Bros were taken into custody and jailed on the pretense of probation violation and DOC violation(s). LE wanted them sitting in jail because LE wanted to strongly "encourage" them to cooperate with LE (jailing a person has a funny way of making people much more cooperative with LE).
But, this is all just THEORIES and SPECULATION.