It sounds like the "bumps/roughness" you're seeing are "orange peel".
It could also be a "sandpaper" texture. That's usually an indication of a "dry" spray. I.e. the material is drying before it hits the surface. It could also be dust nibs which are contamination in either the air (which I doubt because you said you set up a makeshift booth) or in your material (make sure you're straining it.)
Orange peel is caused by the material not atomizing sufficiently. Basically you're getting "clumps" of material hitting the surface that don't "flow out" into a smooth, even liquid film.
Make sure your material is thin enough. Get a viscosity cup to measure it and thin it down until it matches the recommendation from your gun's manufacturer. This is the #1 cause of orange peel. Most paint is designed for brushing or airless and is too thick for HVLP. Latex paint in particular is way too thick to use with HVLP.
Make sure the material is well mixed, that your tip set is big enough, that your air is all the way up (at least to start), that you're setting your regulator while the air is flowing, and that you're not too far away. Also make sure that the bleed hole in your cup isn't blocked with old material.