I've gotten a lot of use out of a wifi inspection camera:
https://www.amazon.com/gp/product/B07MV6X4M4/
The idea is you connect your phone to this via WiFi. This lets you prop the phone up somewhere you can see it while jiggling the camera probe around. The kind that connects directly to the phone are a hassle because you invariably need to wiggle the probe cord around at angle and end up knocking it out of the phone (which then falls, and breaks).
The oil absorbing sheets work quite well. I got a bale of these two years ago and haven't run out yet.
https://www.amazon.com/gp/product/B003ZHUV18
I keep a few resting in places that might have liquid appear, but might drain and be otherwise pumped out. These cloths catch the oil and let any water pass.