Congrates Bob on joining the hobby (or trade as it may be for you). The photos below are of me THIRTY YEARS AGO this month when I was 16!
Bob, the lead you are using is wrong. The "Body solder" used in autobody repair is a mixture of lead and tin. The tin is needed for durabilty. You will see it called "80-20" or "90-10". This is the lead vs tin content, as in 80 percent lead - 20 percent tin.
I have to tell you, learning to lead is great, it is a lost art. If you can pull it off, that is wonderful. But don't get all hung up on it. Modern plastic fillers are in my opinion as good or better than lead. It just isn't the "bondo" of days gone by.
First off, lead if applied even a little improperly is a failure waiting to happen. You use acid for flux,and wax on the paddles. Acid and wax, two things you don't want under your paint! So nuetralizing it is VERY important.
Modern plastic filler on the other hand if used anywhere near properly will out last both you and I. The truck will be rusting away in the wrecking yard, both of us dead and gone and the filler will still be there.
Again, welcome to a great hobby/trade.
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