When using Fox Tail Butt Plug, lots of lubricants should be used, especially lube that is designed specifically for anal play, as it is thicker and lasts longer. Silicone lubricant should be avoided with fox fur as it can ruin the natural fibers.
A thick water-based anal lube like Passion or Astroglide is recommended for Fox Tail Butt Plugs as it is easy to wash out if it gets on the fur. Water-based lube is perfectly designed for anal play, and is natural and non-irritating.
Avoid using desensitizing creams or sprays as well, anal play is a pleasure that should be fully experienced, and not being able to feel can cause injury.
This are some of the best water-based lubes. This are some of the ones I would recommend (and use). They are also often recommended by many happy users.
This Astroglide is glycerin and paraben free lube. It’s water-based anal lube specially made for allergic free anal fun. Get it here
Passion is high quality all natural formula water-based lube and can be used with all kind of sex toy materials. You can find it here
System Jo is water-based lube that contains no oil, silicone, or wax and washes off easily and is also 100% latex safe. Find it here
Another quick advice. I would recommend that you periodically change the lube you use. Your body will over time get used of the lube you use and lube will become a little less effective.