Using lead to fill trim holes
Just keep in mind that it's really easy to create more damage than positive progress when you're working with the lead. Heat can cause a lot of distortion. It's important to prepare the surface the very best you can before you start. If you don't you may find that you will be putting the heat on your panels much longer as you try to get the tinning and lead to stick. - And the longer that heat is there, the higher the probability you'll create distortion.
It's a lot like welding on a patch panel. CONTROL YOUR HEAT!! I hope you're successful but be careful.
'Back in the day' before the hazards of working with asbestos were known, I used to use a product made from it that was in a wet paste form. You'd apply it to the areas around where you were using a lot of heat so it would absorb the heat like a heat sink. It did help prevent distortion. I don't know if a safe alternative is sold these days.