How to restart tube amp and pre in boxes for 2yrs

Yeah, have some load on the amp if you do my method. For a tube amp always have a load (speakers) on it if it is turned on. For solid state amp or preamp, this is not neccessary.
For a tube preamp it is also a good idea to have the outputs connected, thought not nearly as important as a tube amp.
Yes my method is the cheap way to do it. If you have any doubts, get the Variac.
My method works, but it is just a cheat. On the cheap. It works, and accomplishes the same thing as using a variac (forming the capacitors) but is not as theoretically 'perfect' as using the variac.
So choose your method.

Two years is not a long time to be sitting idle. The electrolytic caps should be okay (assuming they were okay going into storage).

You should not have a problem with speakers not attached if you don't put a signal into the amp.

Elizabeth's approach would be a not to difficult to implement safety measure. Be sure to have a reasonably long time between turning on the amp again. Some tubes hate being turned on again immediately after being turned off. If I do that with my power amps, I sometimes get a tiny flash from the rectifier.

Important that you bring the amps to room temperature of 72 degrees for at least a day. Never start them otherwise. Second the load comment.

Larryi..You're actually at an advantage having a tube rectifier. The tubes running off that rectifier (high voltage) have a nice soft start. No tube will conduct until the rectifier starts conducting and turns on, minimizing the inrush current. Tube units with solid state rectification are a different story. Voltage appears at the tubes before they have a chance to conduct. The inrush current is not minimized and there is no soft start. That makes it much harder for old capacitors to form up, and puts a strain on the power transformer. The flash you see on the rectifier is because there is no soft start for the rectifier. It provides a soft start for everything in the circuit it feeds.

Hifigeel1,

Yes, the rectifier does act as soft start for other tubes and for the power supply caps.

Perhaps you can help with the issue of using a variac for tube gear that use solid state rectification. A friend had such an amp that had problems with diodes in the bridge rectifier blowing up. The manufacturer stated that both over-voltage and under-voltage could be responsible for that happening. Since the use of a variac would create such under-voltage situation, I am wondering if that claim is really correct.