Cool, I put “work with” - PM if you want a change! 
My suggestion is that, since you’re going up against a canny fellow who has his ancestral faith and tribal customs intact, a very powerful thing (and hence the one under regular attack around the world) you may want to summon Duke Cohzier, which is familiar with the Abrahamic god and its currents, and was active in combating the troll god and protecting people from the malevolent effects of the three main monotheistic faiths.
Belial also has a bigger dislike of religion than almost any spirit I have encountered, and along with Azazel, you have a good triad for knowing the kinds of shielding he has (probably inherited, rather than consciously used) and influencing him towards seeing the reailty of the situation.