My DD is also very full on, and in the early days was quite rough with DS. Unless i was just there, within arms reach, i had to seperate the two of them just to keep him safe. She could also be incredibly loving towards him, but this wasn't all the time.

As DS has become more able to interact with her, she is getting more positive attention from him and doesn't feel the need to poke, hurt him etc just to get the reaction.

Time had the biggest affect on change, but giving DD concentrated attention (doing craft or jumping on trampoline) seem to fill a need in her that reduced the destructo moods. Giving her special time with DS also helped. So, having ds sit on her knee, or have a cuddle - she only needed about 20seconds and she was ready to do something else, but it helped foster the bond in a positive way.

Her reactions were/are quite immediate or in the present time, so i doubt that time outs etc would have had much impact, but i don't do them so couldn't say.

it is tough, but it has got better here.