Get the biggest tip that you can fit into the iron, and try that. You will probably need to order it online.

Use a little solder on the iron tip to help conduct heat into the connector.

Pre-tin the wire and immediately try to solder it in the connector while it is still hot, instead of letting it cool for a few seconds. This will decrease the amount of heat needed to be put into the components to heat them up enough.

Usually a bigger tip is the answer, when not possible, add 50* to your iron temp. Always try a bigger tip first, unless the task somehow prohibits one.

Remember the TK950 is a rebranded Hakko, so get hakko tips.