Of the options you listed, I suggest powerwashing and brushing with a wire brush. Unless the paint is severely chipped it should be fine. Be aware old coatings are likely to include lead paint. Heat stripping may be hazardous. Also be sure to collect paint chips and dispose of properly.

To recoat, I recommend a stain sealing 100% acrylic primer (pretint) followed by 100% acrylic finish coat from a reputable manufacturer. This will avoid bleed-through, provide a good tack and will provide a flexible paint that will resist chipping or delamination from temperature changes. A professional paint store can provide more information and suggestions.

This is not the best time of year to be starting an exterior painting project in Pittsburgh…. Yens got too much chance of missing a stillers game! (Just bein nebby)