Yes an aerosol can of light colored primer will work as a guide coat . This will show Highs & Lows when you run a block over the panels .
Sanding in an X pattern as it will not cut groves the size of your block in the panels Use this method through every blocking process !

I would not use a spray can primer for priming your body work , use PPG's K36 for your priming & blocking process , and I would stick with PPG products as this is what your ground surface is , I am not a big believer in mixing products as you never know what is or is not compatible with each other . Even though many mix products with great success .
It may take a few primings and blockings to get it ready for paint .
PREP work is 80% of a paint job .

When you have it ready for paint I would leave it in the K36 primer and let the paint shop use the sealer and base coat and clear . Hopefully finding a shop that shoots PPG .