I have used assisted feeding on numerous occassions with good results, and without a lot of stress or any danger to the gecko. What you do is let your gecko sit ofn your hand, pinch off the head of a mealworm, pull out the brown string of guts (this is not harmful, but geckos do not like the taste of poo) , and squeeze the whitish-yellow insides onto your fingertip. Put to goo to your gecko's nose, and keep your finger there til your gecko starts licking. You can also dab small amount on top of the nose for the gecko to lick off. Do this with several mealworms in a session.
Force feeding is dangerous, we had someone come on here who broke their geckos nose doing that. If you ever have to do it, make sure you use proper technique (same as administering oral meds). Hold the geckos upper body up to the top of the head. Try to make sure the geckos front and back legs are supported- less stressfull for gecko and will squirm less. You take a q-tip or other small stick and press the bar against the side of the gecko's mouth. You are NOT trying to force the gecko's jaw open, you are triggering a response that will make the gecko open its own jaw. You should NEVER force a gecko's jaw open it will break. When the gecko open its mouth slip the rest of the bar in so the gecko can't close its mouth, and administer babyfood/insect slurry/meds via oral syringe. Do ot feed too much at once, maybe a quarter of a small oral syringe to a half at most of food. This IS very stressful to your gecko, and should only be done when medically neccessary- e.g. to administer meds and ensure correct dosage, or if assisted feeding fails and you need a stool for a fecal to diagnose illness, etc...