How do you distribute fuel equally on a rocket?

[TIMEFORSPACEPEOPLE]

Im with a rocket that has 12 fuel tanks on the sides of it, six large ones, and six smaller ones on top of the large ones. The rocket is orbiting Vall currently, and it needed more fuel to land on it so I sent another ship to dock with it and refuel.
Once docked the problem of having to fuel each tank equally popped up. There seems to be nothing that helps with that. All I could do was refuel some tanks, but the other tanks won’t have the same amount of fuel.
Which I also think is the reason that causes me to spin uncontrollably whenever I throttle all the way up because of some tanks being heavier than the others thanks to them having more fuel!
How am I supposed to do this?

[Streetwind]

To transfer fuel, you select two tanks, right? One source, one destination? Well, the trick here is that you don't need to stop at two tanks. You can select as many as you want, and then do 1->N or N->1 type transfers.

In your case, you would select your six large fuel tanks, and then one of the tanks of the refuelling vessel. Then you order that one tank to empty itself. Its contents will be equally distributed to the six other tanks. Afterwards, if the refuelling vessel has other tanks too, you deselect the empty one and select a new one, while still keeping the six destination tanks selected. And then you just repeat.

In case you ever encounter a situation where one of your ships has tanks in hard to reach places, or just a really large number, you can also use the resource overview window in the toolbar to select a resource, which will select all tanks that contain this particular resource.

[Stone Blue]

If youre open to mods, theres a couple that make this easy, and have a lot more flexibility/functionality.
TAC Fuel Balancer, for one.

 

[king of nowhere]

@Streetwind has it right for what you should have done.

But now that you already transferred fuel unevenly, the only thing you can do is manually transfer fuel between tanks to try and equalize the weight distribution (you do know you can stop a fuel transfer before a tank is full/empty, right?). And learn to transfer fuel symmetrically for the next time

By the way, this is the reason whenever I have a tanker ship (i.e. pretty often in my missions), I make sure to give it plenty of reaction wheels, so that it won't spin out of control even if the thrust is a bit off-center.

[TIMEFORSPACEPEOPLE]

 Problem solved everyone, thanks!