So how do you fix a crystal leak anyhow?
With a ceramic sub, carefully. If the crystal gasket is leaking, the first step is to try and reseat it. The leak could be due to the crystal not being pressed in correctly, or due to issues with machining. Because of the ceramic insert, this is a task you might want to defer to a watchsmith for.
As far as the soapy bubbles, this is not recommended in a dry pressure test and can damage the equipment. Also, by adding soapy bubbles, that could potentially introduce moisture in the case. A dry pressure test only looks at the deflection of the crystal by first pressurizing and then depressurizing the vessel. A positive deflection of the crystal is normal. The concern is when a vacuum is introduced if the deflection of the crystal swings to negative (IE the pressure inside the case drops below baseline at 1 ATM), then you have a definite leak. Only a wet pressure test will allow you to pinpoint the source(s) of the leak. if you have a confirmed leaking piece, it would be advisable to remove the movement. If you are unsure, you can test with the movement in place, just be attentive and if you see a steady stream of bubbles, pull it out of the water before the pressure inside equalizes. Water will not enter until after pressure equalizes. Bear in mind that some air might be trapped under the bezel, so don't panic if you see a couple of large bubbles develop. A stream of small bubbles are what you are looking for. I posted a couple of random pictures I've taken of pressure tests for your reference.
My 088, you will notice one bubble forming from under the bezel....
LMPO, if you look closely, you will see one bubble starting to form from under the bezel by the crown.
WM9 yachtmaster
My 243. This is the most pronounced case of bubbles from under the bezel I've encountered. I tested it a second time after this and it passed without any additional bubbles, so they were all from under the bezel...
