As heating your vinyl parts for assembly or disassembly is very common and occasionally required I thought I'd make a comment about the method I use to do so as I have not found it mentioned anywhere and am not a fan of the usual hair dryer method.
Note that if you have others living with you it might be a good idea to have them agree before using this method as I am using the oven more likely involved in baking, making Lasagna or your festival turkey.
I put a support at roughly middle height, lay a towel on it and switch it to some entry level( low) temperature, say 50°C( 122F for the non-metric folks) and then put the part(s) onto the towel; you can always use a little more temperature if you feel like it, but I suggest you start low.
In the attached photo an Obitsu shin skin was heated for a few minutes before I took it out wearing a cloth glove and assembled it with the unheated foot/ankle joint combo.
While heating in the oven may look a bit as overkill, it does have a few advantages - imho - namely: low temperature, very even heating, low chance to burn your fingers.
I hope this will help some, though those skillful with the hairdryer or other methods are likely to remain using them.