I have been grinding up beaver castor and chopped up fish in an old blender, but I am having trouble getting it how I want it. The blender even started smoking on me the other day so I just stopped. So what kind of blenders does everyone use because I obviously do not have one strong enough.

Try a hand grinder

I was advised several yrs ago to use food choppers, and I've found them great.
Get 3 or 5 cup choppers for $2-$3 at the thrift store, and I keep them dedicated to specific critters.
You can always use Pulse mode or go all out.
I think they are geared better than blenders actually.

Bucket, drill, paint mixer. Problem solved.

You can also just chop it up with a hatchet or knife. I will grind fresh deboned bobcat meat in my good grinder i use for deer, but only if its fresh and only just meat. I have a LEM 3/4 horse commercial grinder. It can grind about anything faster than i can feed it and never bogs down. But its pricey too. I freeze castor and oils sacks and let them thaw just enough that they start to get soft but still mostly frozen and just chop it up in tiny pieces with a hatchet. Quickest and cleanest way ive found to do it and dont have to worry with drying the castor and having a dedicated food chopper. Ive tried cutting up thawed castor and oil sacks. It is just a pure mess and aggravating.

That's how I mix mine, after its been ground/chopped.

Thanks!