You can keep track of the scenes that are added by looking in the changelog file. There is one inside the zip file that includes the whole game.
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That is of course just for the added scenes. It doesn't explain how you will get those scenes. The only thing I can say, because I have been following this game for a long time now, is that certain scenes are connected with specific outfits (for example, in order to have Megan "service" Dean Hubris she needs to wear the Red lace outfit in her daily clothes) and since you can control what Susan wears through her wardrobe maybe, through trial and error you can see the spitroast scene again. Or you can go to the respective update version and check when the spitroast scene was introduced and check the then outfits assigned by the dev.