I cannot imagine hot glue being appropriate - it's for attaching trees to a layout, and the like.
===========
The CA ("Super Glue") is almost certainly what the factory used. It is typically not very "residue prone". If you remove the boiler and get at it from the underside you may be more comfortable, but first you have to remove the boiler...are you comfortable with that?
It's just a little glue; wont hurt the paint; use a toothpick; don't use much.
Too much CA is actually counter-productive, anyway.
Practice. Get a scrap or 6 of something small. Try a few times . Get a feel. Beats a YouTube video. (Really?)