You really do not want any kind of solvent that will leave a residue, and methanol is the preferred cleaner over alcohol. The problem with methanol is that it is highly flammable and if you need to have if you buy it online or need to travel with it, the airlines have obvious objections. So a company that's been making sensor cleaning (which works well on mirrors too) Eclipse has come out with a non-flammable solution called Aero-Clipse.
Photographic Solutions Aeroclipse Digital Sensor Cleaning AERO
I wouldn't recommend Q-Tip swabs unless you're desperate; cotton fibers/lint can come off on the mirror or mirror box and eventually onto the shutter or sensor. Ideally you'd use one-time-use lintless sealed swabs intended for cleaning without leaving fibers or lint like the ones included in this Eclipse kit.
Photographic Solutions Sensor Swab ULTRA Kit (Type 2) UK2 B&H
They come in various sizes. The smaller ones are more versatile for use on not just APS-C sensors, but if you're shooting FF, you can find larger swabs.
Keep us posted and tell us what worked or didn't. Good luck.
BTW: I have found that no camera is IR (insect resistant) if the lenses and cameras are not always capped. You just gave me a great idea for an art project. Put a whole colony of ants in a camera and dub the camera Antax.