Hair dye help!

Hi there! I’m dying my hair and doing something new so wanted to come on here for advice. I have watched some videos but they don’t go over my specific question. So currently my hair is like 2-3 different colors. I dye it black all the time but my roots are pretty grown out because it’s been a while and my roots are a dirty blonde.

So what I’m hoping for is to re- dye most of my hair black but add a red money piece. Now I have my friend helping me and she did go to cos school but doesn’t have her license and doesn’t 100% know how to do this. I’ve watched a Brad mondo video but he’s just showing how to create one. My question is with doing the black and the red how should I start? I tried to google and saw I should do the money piece first and then do the black? If anyone’s ever done it before can you maybe give me a step by step? I’ve only done color in my hair once when I was like 16, it was professionally done so I didn’t do it. I’ve always wanted to color my hair different colors and I’m super excited! Thanks in advance for any advice

Also to preface we are bleaching/ lightening the money pieces of course!