I stumbled across the ReaFir plugin in Reaper the other day when working on my soon to be released NTS-1 Video.
It worked well in helping in cleaning up my most recent field recording with the mobile setup (Volcas(FM/Sample), Circuit, NTS-1)
(Next time I need to capture the hum after adding in the NTS-1 effects to make it work even better!)
Hope it's helpful, or you at least enjoy the beautiful scenery I captured from Victoria BC =)