I am responding a bit late to this post but here goes. I sold Por-15 Products for ten years and have used some of the paints and rust removers on my cars to include Boss 302, two '70 Corvettes, and Porsches.
Metal Ready, a Por-15 product will do a fine job on rusty bits. I let them set overnight in the juice and put on rubber gloves and get to scrubbing with the small brass brushes I buy from Harbor Freight (my favorite store for cheap stuff). They (Harbor Freight) also carry a rust remover that is very safe and it works o.k but I stay with Metal Ready. For all I know the other acids work well but this is what I am used to. A bench grinder with a mild brush is just wonderful for small items even with threads. I put on my goggles (safety first) and hold the item with a pair of angled pliers just barley touching the item to the moving brush. Works everytime. Currently doing a '63 356. Amazing how much room there is in a 356.......amazing
If anyone wants to know about the Por-15 paint (one part urethane) I will be happy to write on the subject. Keep in mind I haven't sold that line for five years but not much has changed. I now am required to pay retail.....damn
Also while I am aimlessly writing, another fine product line is the Kriol Company. In my unbiased opinion they make the finest penetrating oil on the market.
Por-15 products are not cheap.....but I only like doing the project once so I pay.