How to get cat less afraid of brush?

So in October I moved apartments and brought the cats that's I've been taking care of in backyard for 4 years with me and made them in door cats. They are Cleo (female) and Athena (male). I got them both fixed 2 years ago. They learned quickly to use the litter box and so far things have been going well having them inside full except their fur sheds everywhere. I recently discovered a deshedding brush and bought one online and it came yesterday in the mail.

Athena has always been more comfortable with me. I can pick him up and he will lay on my lap and he never has a problem with me petting him. So brushing him was easy. However Cleo has always been more standoffish towards me like I can't hold her and can only pet her at certain times and it's taken longer for her to get comfortable in her new home. So I knew she would be harder to brush.

So what I did yesterday was I waited until Cleo was sleeping on my bed since she is more comfortable around me when I'm on the bed. I got on the bed with her and waited a few minutes and started to brush her. She immediately woke up and let me brush her for a few minutes then she ran away. So I waited again for her to go to sleep on my bed and I tried again but she immediately got up and ran away. I tried one more time and she did the same thing.

I read online having her smell the brush so she can realize it's safe but I think she will immediately run away if I put the brush close to her. What else can I do so she isn't afraid of the brush? Thank you in advance