Hi Glock,
This is a little late, but hope you have had success with your UH60 RTB problem.
The ref that Cyclic provided should provide a good basis to do the basic RTB. If the blades and machine are in reasonable shape then the procedures outlined therein be pretty straight forward...just print off the charts and worksheets and go for it.
Don't want to tell you to suck eggs, but not sure of how much experience on Uh60s you may have. Just be advised that the 4 per rev tuning is different to the RTB but commonly carried in conjunction with the RTB. But the first priority is to get the RTB within limits first.
Often, as the main rotor became smoother and below 0.1 IPS, it often made the 4 per rev vibes much more noticeable to the point of thinking that the machine is actually getting rougher.. This link may help
https://www.rwas.com.au/rotor-track-and-balance-rtb/
Scroll down to "Nper Rev Vibration"
Also if the blades are getting some time up on them and depending on their service history, be cautious if the move lines begin to move tangentially rather than close to parallel to expected move lines i.e. if the move line doesn't track toward the zero origin but moves tangentially past the origin and the minimum achievable vibe level is still excessive (>0.2/0.25ips) It may indicate a span moment mis-match which may need the blades to be statically balanced and tip weights adjusted. to bring the span moment back within limits.
See this link for explaination:
https://www.rwas.com.au/the-blade-problem/
I will PM you a guide on how to create you own polar chart if all else fails....
cheers
RG