Where I used to work, defense app, the techs used blue loctite on everything. IIRC, when they serviced things, they used acetone on q-tips to clean off the old loctite. Also, heat softens the loctite, so you could heat the bolt while trying to screw it in; Steel transfers heat poorly, so I would heat the end of the bolt threads directly, then try to screw it in. I use one of those pocket torch-lighters. I wouldn't try to heat the rivnut directly because you could goof up the paint.