Re: bent vinyls
using the oven is ridiculous for vinyl, that's probably the worst possible method, next to impossible. you are almost guaranteed to detsroy the record completely. it is however the best way to de-warp 78's.
you really need two pieces of glass, or similarly perfectly smooth and flat surfaces. you need to heat up the record while it is sandwiched between 2 smooth surfaces, so there's little else but glass that will work. heating up the record somewhere and then moving it somewhere else to be flattened is almost guaranteed to fail.
i'd never heard the iron idea, it sounds somewhat promising.
sunlight is best but depending on how sunny it is, 5 minutes could be way, way too long. the record does not need to be very hot at all to become slightly maleable (that's why the oven idea is retarded)...and equally important is a long cool-off time....don't even think about removing or even checking the record until you are sure it's completely cool...if the record is still even slightly warm, it will warp all over the place if it has any space to do so...
keep in mind how easy it is for a record to become warped -- a few minutes in direct sunlight, even inside a cardboard box, can do it....so you want to be very subtle and gentle in your attempt to de-warp