sayerville and nigelslaterfan
Have no fear!
Old, manky socks, pants and underwear, look just as joyful when folded and filed! Some of us can't afford to replace everything at once! 
Clearing out our parents' home is probably the most daunting, emotional duty we will ever face, and I can see that kondoing our own sentimental stuff is not something we would want to tackle immediately afterwards.
Oddly, dealing with our parents' personal belongings, respectfully, can help us to be gentle with our own sentimental stuff, later.
Following MK's method, gradually builds our confidence to deal with our more difficult possessions. Decisions about what to keep, become easier, as we learn to recognise what exactly makes us feel joyful.