I've used KBS diamondclear for the 3 playfields I've done, very happy with it.
Dave Brennan recently did a series on the turbografx7 facebook page where he touched up and then cleared an alien star using the KBS stuff, well worth a watch even if you don't follow what he does exactly. here is the group page, restore stuff was back in early May. https://www.facebook.com/groups/227942975051203/