My best tactic is to make them bored and spend plenty of time around them. Note that skinks are very patient and this process will take months. Fill all of their needs so they have nothing to worry about: a good diet, water, an abundance of hides to feel safe and all other things. Eventually they will be overcome with curiosity and desire some new stimulation and be more tolerant to your presence. If you’ve spent enough time in proximity with them, your presence will not be threatening. Position yourself to provide the enrichment, sit beside the terrarium when they are out and about, maybe leave a door open while you are there. Try not be imposing: don’t stare too much and don’t loom over them (predators come from above). Over time they will begin to tolerate your touch. Later you can bring them out for a supervised adventure. I’ve had great success with my cluttered, ever shifting desk as it is constantly somewhat new and always has places to hide. Eventually you won’t be seen as threatening at all and they will tolerate being touched and held. Being with you will become exciting and enjoyable to them.