Tony M,
It's hard to say what primers are compatible for spraying under Shieb's top coat. I've never had much problem putting any kind of paint over lacquer.
They make a primer/surfacer in lacquer that should be no problem for you to spray.You will also have to have lacquer thinner for it. It thins at 100 to 150 % to the paint, plus you'll need it to wash out your gun. I clean my gun by first dumping out any excess paint in another container, then I usually wash out the cup and the underside of the top of the gun. I keep a coffee can to pour my dirty thinner in. Then I put some thinner in the gun a open the adjustment up on it and spray the lacquer thinner thru the gun. After you have sprayed some thinner thru the gun, take a rag and hold it over the cap tightly and spray the gun. After you are done with this, remove the cap and make sure it is clean in the cap, make sure holes thru cap are clean. If not wash cap out in lacquer thinner till it is. Replace cap and wash out cup and any places that any paint still may remain. I use a small 1" paint brush to wash gun with.
Have you talk to Shieb about what would be compatible with their product. When I worked in a bodyshop we used a two part acid primer which was mixed 50/50. This etched the metal and layed down a thin primer film, didn't fill anything thou. It dried in about 1/2 hr, then we used a primer/surfacer that was a 3 part mix. It was used to fill minor imperfections and scratches. We sanded this then it was ready for base coat/clearcoat or acrylic enamel with hardener.
If you use the lacquer it would be a good idea to use a metal prep on any bare metal you have, it helps remove minor rust in pits or scratches and etches the metal to make the paint stick better. I hope some of this helps.
