http://www.soomal.com/doc/20100003594.htm
The article is in Traditional Chinese, but the pictures are self-explanatory. Each picture of the series represents each step of the whole repair procedures. The new trick is to turn further from the underneath of the motor module, which should be further dismantled, just in case if the screw on the top is locked too tight and cannot be turned. See the two key diagrams for what to turn:-
As for the force applied, the author hints that you should try it by yourself - do not apply excessive force and try different directions, depending on how the SDM motor and the associated gears are locked.
Good luck if you are yet one of the SDM failure victims and still want to try the repair DIY! As for me, I have none of the Pentax SDM lenses, just because the SDM issue has been so infamous but then the service and support of Pentax to deal with the issue usually sucked as widely reported, so that I have been avoiding it as far as possible over these years.
Related (Oldest First):-
Repair a Stuck SDM Yourself!
Repair a Stuck SDM DIY - An English Guide
Hair Dry and Repair the SDM! :-o
SDM DIY Repair Method Also Works for the DA17-70
Improved DIY SDM Repair Method!
Pentax has Modified the Design of the SDM Used in DA*16-50 and 50-135??