I could never find a way to slow down animations, this is also on my wish-list, an exhaustive web search gave me no decent results. However, there is a setting in Wicked Whims which will allow you to change the duration* of sex scenes, the default time-frame is too short. MCCC will allow you to slow down or speed up your game but it warns of consequences for doing so.
*Wicked > Settings > Sex Settings > Sex interaction settings > Choose Player Sex Duration OR NPC Sex Duration.
Player Sex Duration: I have Time Limit ON and I set "sex interaction duration to 20"
- If you turn time limit off, they could boink until they DIE? I have not tried it, LOL
NPC Sex Duration: I set at 2 which shortens autonomous NPC Woohoo.
If you lengthened sex duration drastically, you might want to change some Sex Progression Settings otherwise you could experience ending animations prematurely. (Wicked > Settings > Sex Settings > Sex Progression Settings )