How to Dye my hair with highlifts

I have dark brown (practically black) hair. I want to dye it without bleach, a video on TikTok said I could use ignora royal highlifts 12-21 and 12-0 (Schwarzkopf) with a 30 and 40 developer to bring me to a nice warm chestnut brown. I want like a Natalie Portman chestnut brown. However I’m nervous to do it myself because I don’t see enough tutorials or information regarding how I can do this at home myself. I’ve looked at salons (NYC) and I’ve gotten quoted 295$ for just this simple chestnut brown in multiple salons. Does anyone have any advice or a video I could watch with information? I’ve done research but I’m still is unsure…it would save me a ton of money to do it at home. I’m unsure because of the time I have to leave it on my head along with the heat so the bottom and mid section of my hair dye a lighter color to avoid having my roots complete orange before the ends of my hair could get lighter. Any advice will be helpful!