In a nutshell, get their attention, give them clear explicit instructions and tell them the consequences. Then stick to it.
Keep your voice quiet and calm. Get down on their level. Reflect back an understanding that they might not want to but that's what we need to do. No negotiation.
Notice/praise the good. Expectations and consequences should be clear and predictable.
The 1 year old will learn from the 5 and 6 year olds. The 5 and 6 year olds will already know how to do this from school.
When you shout at children they stop hearing the words and only hear the volume/anger. The less you do it the more effective it is if you need to eg in dangerous situations to get their attention.
Some children respond really well to visual cues too. So even saying stop and putting your hand up (other makaton signs are available for reinforcing) can help them and are quite often used in schools.
And, tbh, I've had parents come and speak to me who have asked what we do in school and what works so they can do it at home.
I think it's crazy that we, as parents, are just expected to instinctively know how to do these things.
Some people will, some people try things and just find something that works but there's no harm in asking someone else for suggestions.
I wasn't a shouter. My children were pretty calm as a result. One was a naturally easy child and the other was far moe challenging. Shouting would.have just made her worse and would have been counter productive.
If you shout, you end up just having to shout louder and more often and, tbh, who wants to spend their days just shouting at their children?