Dorthy worked with FM at first, and appeared in a few of their batch-clip videos. The one I remember most is her being tied face to face with Loreli and them being duel tickled.
She then started her own production company, and under is she made several tickling videos as producer and occasionally appeared in them. I had two customs done with her with Cathryn Beaumont, where Dorthy was the Ler, and in the second there is a scene were she is Lee to Cathryn. I remember her being Ler to Darla Crane in some clips also.
Around the early 2000's she retired and the SLAMM work you note is some the last we've seen of her. Slamm does shoots with the classic models as a rule, and occasionally does tickling sets among their bondage work. He's a nice guy and if you find him on Deviant Art you can see what he is currently up to. He seems to have a lot of older unreleased photo sets and vids that he is slowly trickling out.
I think Loreli has talked Dorthy into doing a shoot here and there for her own company in the last few years, but that is bondage and DiD stuff so not what you seek.
Mostly it will be the old FM, and Dorthy's custom stuff that will fit your bill. The FM can be bought as individual clips on thier site once you find it, and Dorthy's stuff is still for sale in a few online stores, but it will be a hunt. The Custom with Cathryn was named "Cathryn's Tickling Torment" Here is a link to promo images of the second one where Dorothy gets tickled:
http://www.ticklingforum.com/showth...kling-Torment-Part-II-F-F&highlight=Cathryn's
It seems to still be buyable here:
https://www.hotmovies.com/video/55801/Cathryn-s-Tickling-Torment-2/
Best of luck
Myriads