I tried once to put fluid in a tube. I bought the liquid inflator from TSC (slime brand) used a 12 v pump. WHAT A MESS!!!!!!!!!!!!!! The tube got sucked in the rim and I couldn't deflate the tire. I don't remember how I got the rim off. I said a lot of different cuss words that day . It was a new tube. Maybe I should of used a used tube. There is always air in between the tire and tube maybe that was the problem. Maybe fill with air first and let the tube get to the rim and tire shape then put the fluid in.
But on a tubless rim/tire. I make sure the bead doesn't leak and then I pop 1 side and pure it through the popped bead. You can get 5 or 6 gallons in an 8.5 tire. I use used antifreeze. Won't rust the rim and swell the tire. WWF will eventually rust the rim and ruin a tire. It will take a long time but it will. I just put an ad on craigslist for used antifreeze. I collected 55 gallons in about 2 months. It's also good to 20 below.