If they don't seem interested in a treat, or are even scared by the approach of it, and they are interested in the stick itself, you might try just using it as a reward. If they are willing to approach the stick just to check it out while you are holding it, GREAT! Talk softly and happily to them, praising them. Try gradually sliding your hand up the length of the stick, so that the end of the stick for them to investigate is closer and closer to your hand. If they are happy just nibbling on the stick and playing with it, just work with that.
Do they like millet? That tends to be one of the favorite treats for birds, especially the little ones. Do they know what it is? If they haven't had it before, hang a spray of millet in the cage for a few days, until you see they are eating it and enjoying it. Then, take it out, and only offer it during training sessions. Once they realize it's yummy stuff, they may be less scared of it.
Chapala also posted this video on the budgies forum as well.
YouTube - Training Your Budgie(s) It is another approach, and even though it has budgies in the video, it would work with lovebirds as well. Just remember, as Chapala said in the other thread, this video took weeks just to get to this point where the birds would step on her hand to get the treat.
Patience is the key. There are a ton of different methods for taming birds. Some will work for one bird but not for another. Do lots of reading in books, magazines, and on the web. Just remember not to do anything that FORCES your bird to interact with you. That kind of information is pretty much outdated. Professional trainers use positive reinforcement only, meaning the bird is rewarded for making the choice to interact with you...not forced to do so or punished for not doing so.
Good luck and keep trying! It takes time and patience.
Danielle