This is coming from several years of professional & freelance animation experience working on first person animations for many released projects and games (Non-NSFW) with Blender & Maya
There is no easy way... Even if youre looking on just making or using a pre-made a 1-fit-all walking animation you'll have to tweak it a bit and maybe even make your own multi-rig. Going through courses, guides, tutorials and being in animation servers is going to help you tons but there really isn't any simple way
If you're only looking to make 3D animations like the creators you named you'll also probably have to learn scene making, lighting, sound, VFX work in and out of blender, video editing and modelling incase there isn't a free model of what you're looking for.
If this is just for video game animation you'll mostly only need rigging and animation alongside knowledge on how these two work in the engine you're using
Some basic YT guides that will help you with "easy" animation tho:
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- Basically an easy but almost never perfect way to get basic animations for your models
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- If you find yourself with your hands on some animation data from modding a game or something, you can use this to re-target it to your wanted model
If you're looking for something more advanced and to learn actual animation make sure you join 3D animation & modelling servers so you'll be able to communicate with people that can either help you directly or provide you with more advanced tutorials and courses. There are also tons of servers dedicated specifically for NSFW 3D creations that can help you, from personal experience I found these servers to be quite unwelcoming to beginners but if you get past that barrier you're golden.
Some places to get you started:
I wish you the best of luck in your journey and hope this helps you in starting your process of someday seeing your own 3D animations used in porn ads!