I have a 4 yr old and a 10 month old, so I'm with you!
What I do it that I make sure to tell the 10 month old when he's doing something that's not allowed - hitting, throwing toys, pulling hair. Does the 10 month old understand? I doubt it. But I think it's important for my older son to see me saying "no baby, we don't pull hair" as I remove his hands from my older son's head. Or "no baby, we don't throw toys" as I take away the recently thrown toy. Of course the baby doesn't get the same punishment as my older son. For example, a thrown toy by my older son gets put away and has to be earned back; for the baby, it just gets put away for an hour or so. But I think (hope?) I'm still making the point to my older son that the rules are the rules.
For the behavior chart - I've done one and it works great when I do it - but like you, I have trouble being consistent. I set it up the same way as my son's daycare. Instead of specific things, it is split into times of the day - morning, lunch, nap, afternoon, dinner, evening, bedtime, sleeping. If he is good during that time, he gets a green smiley face. If he is mostly good, but acts up a little (ie, if I have to tell him 3 times to get his pjs on) then he gets a yellow unhappy face. If he does something really unacceptable (hits, throws a tantrum, etc) he gets a red frown face. I don't actually give him anything concrete for greens. He is thrilled if I give him a ton of praise if we get to the end of the day with all greens. If there is a yellow or red in the day, we talk about it before bed, and talk about what he might do differently the next day so that he can get back to all green again. For a kid that isn't so motivated by praise, you could give a prize for getting all greens for 2 days in a row, or something like that.
It works great, but it's a ton of work to keep up with every single day...