The problem with using glow fuel is that it contains oil.

If the carb leak is so bad that he resorts to using silicone to seal the carb--it will be hard to get a good seal because of the residual oil. Silicone doesn't stick to oil. It will form and flow around the oil, but it won't stick to the metal beneath the oil.

I'd use the brake cleaner.

I honestly think he just needs to squeeze the carb down a little tighter. Once that O-ring gets squished down nice and tight--should be sealed.