I have an anova sous vide. I put coconut oil and the bud in a mason jar, finger tight the lid, set at a temp (I forgot what, it's been a while) and come shake and burp it frequently. I already had the sous vide, so that was no cost to me, but I don't know that there's a better option out there either than maybe a magic butter machine.

I think basic sous vide machine can be had relatively cheap now. It's good for this, but great for food.