PPG Primer Surfacer, Shrink time? Options

[bbrock]

This is a pretty specific question but wondering if anyone has experience or thoughts on PPG K36 vs. K38 primer surfacers. In reading other forums, it seems some people think that because K38 is a high build surfacer, it has a higher solids content and therefore less shrink back. Local shop stocks K36 but has to order K38 which is also more expensive.

Would one month sitting in the sun be enough time for either of these to shrink before blocking, seal, and finish coat?

I realize there are probably cheaper options that are just as good but I'm pretty limited on what is available at the local paint shop and want to keep all the products in the same paint family since I'm a novice at this.

TIA.