Lead finishing

[speedo]

Finishing up the rust repair on a 914-6 and have a couple questions. To correctly repair the chassis, I had to remove some lead in areas. I picked up a 70/30 kit from Eastwood and have watched numerous videos on application of 70/30 and leadfree solder. Aside from the fact that most users in these videos ignore any form of defensive protection ...I feel pretty comfortable prepping and applying either product. Exterior areas that are "surface" are not going to be a problem to file. Given that the 70/30 is NOT sandable, I am wondering how I am going to FILE certain areas to get them ready for primer (door handle recess, wiper recess, hood channels etc). Am I better off NOT using the 70/30 and use the leadfree solder as it is sandable? Or am I better off simply using plastic filler? Downside of plastic filler is obviously you can't use it on an edge, it can shrink over time and it isn't original. I have plenty of experience with plastic...just wanted to put the lead back where it was used.

Speedo