I like to find the location in the fuselage where I'm going to put the weights, make a clay model of the weights, then make a plaster cast from the clay. Melt the lead with a ladle and soldering torch, pour the lead into the plaster cast, then fix the weight in position. Yes I do this in a well ventilated location.

For what its worth, I always believe if you're adding nose weight, you just don't have a big enough engine.

In my experience, most trainers do not need any weight added for balance. They're normally able to balance by moving the battery and reciever.

Brad