Create an action group that has the following actions
1 - Action to copy the feat artist from title to artist:
Format tag field
Field: artist
String: %artist% & $mid(%title%,$add($strstr(%title%,'Feat.'),6),$len(%title%))
2- Action to cut the feat artist from title
Format tag field
Field: title
String: $left(%title%,$strstr(%title%,' Feat.'))
3- a little hygiene
Format tag field
Field: title
String=$trim(%title%)
(as always: try it with one track first before you spoil your collection)