ching, I suggest you to buy a dual-power solder gun ( my one is 40W, can switch to 200W for 30sec ), solder T-plug must be hot enough and in very short time, otherwsie the T-plug plastic will melt. Buy some better 錫線 but no need to buy very expensive "silver-content" 錫線, because the silver type "sounds better" for audio use, RC do not need this grade.
Clean both surface by alcohal to remove oil-layer and ensure it's dry, then apply just a little 松香膏, that's it. The last secret of good solder is to practise and practise !