I have not! so as a kid i think he would have worn the shit out of them until they broke in on their own or used the hammer towel method (hope you got a lot of heel bandaids available johnny boy!) though to be honest, i have these art pieces where hes a teen wearing docs, and im really not sure how he'd canonically even get a pair of docs, you know chief o'sullivan would never have bought him 100+ dollar boots so thats either a gift from Caro, friends, or not canon. truthfully he'd probably have worn general issue black combat boots he got at the local thrift store in his teens.

older john would be aware there are easier ways to break in a pair of leather boots without killing your feet completely, he'd resort to the tried and true way condition your leather and wear double thick socks, and occasionally apply gentle heat (hair dryer method) or toss em in the freezer.

i guess heres another Punk Rock Fact for you-

its best to wear 2 layers of thick socks, your docs /boots should be a bit snug when you buy them, cuz leather stretches and they will end up too loose if you size up (this is also why its not always great to buy leather shoes or boots from the thrift, theyve already molded to other peoples feet and can hurt and fit you very wrong!)! two socks helps protect your feets and push against the boots.

wear them around the house for a few days with your double socks to loosen up the leather, take em off when it starts hurting and extend the time every day. stuff newspaper in em when youre not wearing them if you want to help them maintain stretch. keep those bandaids and heel blister plasters close by.

so the two ways to make it happen a little bit fast is heat or cold. so for heat what you wanna do is get some leather balm (hate to shill a product but doc martens wonderbalm is actually super nice. mink oil works too.) set that aside and put on your biggest fattest socks or double layer, throw your boots on and lace em up real tight. yeah its not gonna feel good. thats ok, youll live probably. now take a hair dryer on its lowest setting and VERY GENTLY and not too close to your boot, heat all the surfaces with it for about 30 seconds per spot (but continuously move the hair dryer). dont do this for to long and only do it once or twice, you dont wanna damage the glue but the heat will help the leather become more supple and stretch faster. leave the boots and and walk around your house again, stretching them out, bending your feet, stand on your tiptoes etc. after they cool, apply the wonderbalm as per instruction to protect the leather.

and finally the freezer method, i use this mostly if my leather shoes or boots are a bit too snug still. fill a heavy duty ziplock bag about halfway with water and make sure its sealed really tight with no air inside. stick the bag in your boots, trust me on this, and throw em in the freezer over night. SCIENCE IS FUN ice expands, take em out the next day and let em defrost and voila. the leather has stretched and softened because of the expanding ice.