Transmission flush

HELP . I have a 2019 tundra limited 4 wd 5.7 engine i think its a 6 speed transmission with a tow package and tow haul mode but no trans cooler. I watched many vids about trans dump and fill without a scan tool , got everything prepped went under the truck to block off the thermostat and didn't find one [Problem # 1 ] put in a jumper and followed directions from car care nut and others but all the truck did was throw a warning light that the truck was not ready to drive [problem # 2 ] i ultimately used digital temp guage but temp is higher on front of the trans pan than on the rear part of the trans pan . The official Toyota procedure would be great .Thanks in advance.