Fighting Siblings Advice

[ManyClouds]

2 daughters 1 3.5 yr old & 1 5.5 yr old. Fights start over usual things like tv & toys. I am at the end of my tether. Youngest will hit & scratch oldest. Oldest won't stand up for herself and lets youngest bully. Oldest seeks me to fix.
I've tried separating, time out, explaining....I can't think of any other solutions.
I'm looking for advice to help with youngest to keep hands to herself. Advice for 5 year old to stand up for herself.
Overall they're brilliant kids but i'm worried I don't approach this correctly.
Is it something I need to work on ? Thanks

When alone remind your youngest that she can't hit, kick, or scratch her sister. Hands and feet are for nice things not hurting people. If she is having a problem with her she can come to you, the solution is never hurting. If she does start kicking or anything later, remind her, "hands off feet off". If she doesn't stop, count to 3. If she still hasn't stopped, time out for three minutes with reflection afterwards as to what went wrong and apologising to her sister. In future just reminding her "hands off feet off" would be enough to get her to stop the behaviour. You may have to keep an eye on them when together for the next little while until the youngest stops using violence. It doesn't sound like there's anything wrong with the oldest's behaviour btw.