The post title is interesting as RTOs won't be done unless you are below V1. I hope.
To keep straight you need to be looking out the front. Also to keep straight it helps to get really familiar with the controls that you will need - I'm a Boeing pilot so the read across may not be perfect but for me I keep rehearsing where my hands need to go for the speed brake and reversers so that I don't need to look inside for them. Don't rush - once the THR is closed the remaining actions can be done at a steady pace without hands flashing around the FD at the speed of light.
JT is correct - if you only do one action it's close the THR. This stops the acceleration, removes the asymmetry and activates the autobrake RTO function. If you're too slow for the RTO to activate then stopping is not a problem.
Finally, you're doing a type rating - it's your instructor's job to teach you how to do things.
HtH