Here's what we have done that has worked well, though we are what I would call "spot weaned", meaning he's still got 3 "special nursing times" but he knows not to ask at other times.
1. We sleep toddler, dad, mama, baby in the bed, so no night access to mama. But he's a heavy sleeper anyway, so we've got it easy in that dept.
2. I decoupled nursing from going to sleep - we nurse until I am ready to stop, then I count to 10 and he says, "And that's gonna be it!" and he's still awake so I sing him some songs or give him a massage and snuggles.
3. I use the "We need to save some for the baby" ruse when I am done too.
4. We have only certain times of day that we nurse (waking, when I come home from work, and at bedtime), and I have noticed that if I get out of bed and get dressed before he's awake, he often forgets to ask in the morning.
Try substitution or distraction - do you want food or a drink? Let's read a book. Oh, can I have X minutes to go start laundry? Try being out of the house at bedtime and having his dad put him down for sleep if that's an option. Think sneaky, evasive maneuvers! Good luck.
