We take tube changes a little further in the bike shop. This method also works great for the impossible 18x1 and 20x1-1/8 tube changes.
Take the entire tire off the rim
Trash the old tube
Run your fingers inside the tire checking for pokey things and check the outside for thorns
Get the new tube and put some air in it to give it shape. Add sealant depending on the application.
Stuff the tube into the tire. You may need to deflate it a little.
Check the rim tape or rim strip for rough spots or breaks. Fabric tape, teflon tape, or electrical tape works well if you need new rim tape.
Put the valve in the hole and work the tire back on the rim. One side is easy, the other side usually needs tire spoons (plastic kind)
Once the tire is on the rim push the valve stem up into the tire to make sure the tube is not caught in the bead
Work your way around the bead squishing the tire to check make sure the tube is not sticking out
Air your tire up to about 20psi looking for any odd spots in the bead where the tire did not seat
If you find a spot, deflate, adjust the bead, and air it up again
Air the tire to the desired operating pressure
On the go or in the field you can leave one side of the tire on the rim and just work the tube in on open side. We can even change tubes without fully dismounting the wheel. BMX bikes don't use tubeless tires. The higher pressures in BMX racing, lack of true tubeless BMX tires, and added weight of sealant keep tubeless out of BMX. Tubeless may work great on your 29'er at 20psi with cushy suspension and weight is give or take pounds; it doesn't work so well on a 20" at 85psi with no suspension and when every gram counts.