Start off at, say, 50VAC and then increase by 50VAC every
1/2 hour until 240V is reached?

First off an ammeter is essential unless you prefer smoke as an indicator.

Secondly, you may not see much B+ until you crank up to maybe 75%. Up
to that point you're basically just testing the filament circuitry.

The premise of reforming caps is a topic of its own. 50-60 year old
electrolytics are generally done for. If you're a restuffer and open
old caps for fun you'd be horrified to find the corrosion that's often
inside of them and ask yourself "why the heck was I so thoughtless to
apply HT to a can full of green crud".

If you do want to try reforming you should do it separate from the
radio. A new HT xfmr is significantly more costly than fresh caps.

Good luck!