You should only clean them if thay are failing and only clean the pots that need it. If there is you use a lubricating cleaner designed for pots and give them a squirt form the inside then work them. You can turn the pot while playing and see if there's any scratchiness. You may set the volume to a sensitive spot and then heat or vibration makes it move to a dead spot. If the problem is worn pots its pretty common for them to become crackly and intermittent. In reality you're only masking the cause and it comes back as soon as the solder oxidizes. If there is a bad solder joint and you flood the jack you clean that bad connection and it may wind up working for a short time. Don't flood the jack, especially if they are plastic PC mount jacks. You can clean them using the same method as above, apply the cleaner to the plug then stick the plug into the jack several times. Next you want to check input and output jacks for cracked solder connections.

Alcohol accelerates oxidation and a white film which is conductive can appear between traces and short connections.

You'll flood the circuit board if the sockets are PC mount and the long term effect is, the protective film applied to boards is stripped away leaving the solder joings exposed. You want to apply it to the tube pins (not the socket itself) when the tube is cold and stick it in the socket when the pins are still wet. Second would be to clean the tube sockets with Non lubricating contact cleaner which contains denatured alcohol. you can save the ends but the wire itself needs to be thrown away.

It will fry it from the inside out and become intermittent just like you're having a problem with before it shorts. Never ever use a guitar cable for a speaker cable. First things I'd do is try a different speaker cable. Volume jumps can be caused by a number of things.

Bias guitar amp tubes bias jumps