Weight painting on model that has a mirror modifer

So I got a character mesh that has a mirror modifer and whatever I weight paint on the right arm copies over to the illusion side. While still linked to the right arm’s bone. I cant seem to give the illusion side its own weight painting.

If my explanation is bad ive found this post that has the same problem that didnt get a awnser
https://stackoverflow.com/questions/59975132/can-i-disable-mirrored-weight-paints-in-blender

Usually you would apply the mirror modifier before doing weight painting.

Ah yes that’s what I thought but the Tutorial im watching still has it mirroring and it seems to be working just fine for weight painting. I guess I just wana keep it to make future editing easier🤷🏼‍♂️

In the video he only weight paints one side (at around 16:00)

Yes thats what im trying to do but my weight paint always mirrors to the illusion side of the body while on the same bone and i dont want it do that.

Make sure that in Mirror Modifier > Data you have Vertex Groups checked (should be by default)

Also, you probably need a correctly named groups with .L and .R at the end

I just saw that each bone on one side somehow had .001 at the end of the name(upperarm.r.001) I erased that part and everything has its own weight paint and its fixed! thank you so much