Welcome to the forum! Yes, that is what I would recommend. Breeders will tell you that the baby bird is already weaned but the truth is that, in the wild, baby birds are fed by their parents much longer than captive-bred birds are handfed. And, even after they leave the nest and are foraging on their own right alongside their parents, the parents (usually the father) continues to supplement the baby's own intake of food for months. I will give you an example, rule of thumb is that the larger the species, the longer it stays in the nest and with the parents so, while canaries leave the nest and start pecking at food on their own when they are three weeks old, they still get fed by the father until they are two months old while macaw babies stay with the parents (canaries don't because they are not social birds, they are territorial) until they are 4 years old and are still getting fed in the beak by the parents until they are nine months old) so, going by that, a Senegal at 12 weeks of age would still be fed by the parents. Aside from that, baby birds usually revert to needing handfeeding out of sheer insecurity and anxiety due to their losing all they know, something that, in nature, doesn't happen to adults much less babies! So, what I always recommend is to make as easy as possible on the baby by not only offering a handfeeding or two at the beginning and stopping it only when the baby refuses it on its own while also offering soft foods served fresh twice a day and leaving them there until the next meal is served. Now, gloop is a soft food so yes, you can use it for the baby but I also recommend offering other kinds of cooked, soft stuff -things like polenta, cous-cous, Irish oatmeal (aka steel cut oats), a good quality multigrain, some pastina, etc. which can be mixed with baby food (only veggies or fruits, mind you, no meat!). This is not only because they provide extra nutrition (the baby food) but also because it's precisely during weaning that babies learn what is safe and good to eat and what is not so the larger the range of foods you offer, the better the bird will eat when it's an adult.
As to training, you won't need to train with a clicker or a target to get him to step up or down, babies always want to be on you (when they trust you) and he will not only step up when you ask him to, he will ask you for it

so that needs no training. What does need teaching is the step down because, as they always want to be on you, they don't want to 'leave' you but that is easily done by asking him to step down for his feedings. I don't use clicker or target and neither do I use food rewards, I get my birds to love me and trust me and, when they do something right, they get praised and loved and it seems to be enough for them because I don't really have 'disobedient' birds. But, when it comes to tricks which bring no reward to the bird from an emotional point of view, you will need to bribe because birds are not mentally programmed to obey or please anybody (it's the kind of social structure they have) so unless you give them something they want a lot, they won't do any tricks. But I do NOT agree with food management! It sounds harmless but it means that you have to make the bird hungry so it would perform and that, in my personal opinion, is nothing but vanity and cruelty. Michael teaches how to train a bird to do whatever you want it to. That's his trade and his business. He has a cottage industry and his birds are part of it so he needs his birds to perform perfectly all the time and the only way to achieve this is by making them hungry. But I don't think that pet birds should need to perform perfectly all the time... And, in any case, all you need to do is keep the bird's favorite protein food as a high value item and use it as a reward ONLY when you are training. It serves the same purpose, it works just as effectively, and it's much kinder to the bird.
As to when to start with the clicker or target... well, I always suggest people wait until the bird is a juvenile. I think that, in the long run (and, with parrots, the 'run' can be pretty long), it's much more effective than starting early. And it's not as if you are not to teaching the bird anything in the meantime. You are! Only you are teaching it the way and the kind of lessons a mother or father would teach a small child. You teach it to love and trust you, you teach it to step up and down, you teach it what "NO!" means, you teach it not to play rough (as when they start beaking and put too much pressure), you teach it what to eat and what not to, you teach it to play, you teach it what his routine and schedule would be, you teach it to go back into his cage, etc. Think of a toddler or a kindergartener and what lessons they learn at home and you would have a good point of reference.
Please let us know if there is anything we are missing or not been clear about.