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

Most tube amps are supposed to be operated only w a load (speaker or resistor across outputs) but I have no idea if this applies to the momentary on-off approach Elizabeth advocates. Best approach is to use a variac and bring the voltage up very, very slowly to allow the capacitors to "re-form" (whatever that means). 2 years is not that long, you might want to ask Chris @ Parts Express who does a lot of modification work on SF gear and I think used to be involved with that company (maybe co-owner??).

Swampwalker, great idea! A variac is the way I do it with equipment that's been off for a few years or more. I will usually pull the output tubes, and monitor the voltages from the tube sockets. Contact the manufacturer just to make sure it's safe to pull the output tubes. With the output tubes pulled I only run the variac up to 110Vac. Internal voltages will be higher because you have the output tubes pulled and you don't want to over voltage the caps. Or let a tech do it for you. I'm on the west coast.

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.