Hi there JustAnything, how are you getting on? I'm surprised no other mumsnetters have replied to your query, given that they replied to the other one about whinging. We must log on at the wrong time of day (or at least a different time of day to the others with toddlers).
I just thought I'd offer you my sympathies again and say that ds1 makes lots of things into a struggle - at the moment it's getting dressed and getting out of the house! I even kept him off nursery a couple of times a fortnight ago just because I couldn't face the constant tantrums on the way there. (It takes us 20 minutes to walk to his nursery if he's in a good mood. I just didn't want it to take half the morning and then have a screaming hungry baby to deal with as well.)
I can tell you two things that have worked with him so far:
(1) star stickers. I give him one whenever he does anything good. I started out putting them on a piece of paper but he prefers to have them on his clothes. It's completely non quantitative, I don't count them up at the end of the day, but it just helps me to focus on what he's done right rather than whatever he's having tantrums about, and he has caught on rather quickly and even suggests that the rest of us have stickers if he's feeling particularly pleased with us!
It goes without saying that if he does useful things regarding looking after ds2 (fetching his clothes or muslin or toys for me) he gets immediate praise and a star.
Then we went to the zoo last week because he had 'so many stars' and he had been 'so good' (still no quantities attached). We had a lovely time 
.
(2) Appealing to his increasing sense of independence. If he won't do something that has to be done (like lying down to have his nappy changed, or getting dressed, or getting into bed, or coming downstairs) I just tell him that he can choose - either he does it himself or I shall do it for him. It may take some repeating before he actually does whatever I've asked him to do, but it does usually work pretty well.
He's so keen to do things himself - one day we were going to go out and I wanted his jigsaw pieces tidied up so I just tidied them up quickly and prompted a tantrum because he had wanted to tidy them up himself. He actually took them out of the box again and sprinkled them on the floor just so he could tidy them up instead of me.
Hope things are going better for you. We went through ages of ds1 being such a miserable and difficult little boy and it made me feel worse to know that we'd caused it, really, by having the second child. Ds1 was so happy and lovely before ds2 came along. But he's coming out of it now.