When you want a easy soldering of litz wire, please make sure following instructions. First of all, you need to set the temperature range of the soldering pot between 430~460 deg. Secondly, it is very helpful to get some paste(=FLUX) before immersing to the soldering pot. It makes easy and fast solder as well as preventing cold-soldering.(The disadvantage is that it generates a lot of smoke. You must prepare an extractor fan.) Thirdly, You may select the dipping time as per your litz wire AWG size. Please click the below URL and check the table how long you have to dip it and other useful information regarding litz wire soldering.