The last car I soda blasted the surface profile came out too smooth per primer application specs. Since you are working only in the engine bay this may not affect your coatings due to them not being directly affected by rain, wind, sun, debris etc.... Improper profile causes poor adhesion and a few months down the road you will have much more chipping, which leads to pitting and peeling. My suggestion would be give crushed walnut shells a try. It worked wonders for me to give a rougher profile after soda blasting and can be reused 2-3 times.
