well you asked about how to make your CURRENT utensil hit smoother, I'm sure you already knew metal homemade pipes aren't the smoothest:detective1:

if there's enough room inside the pipe, you could clean it out by this method: rubbing alcohol and uncooked grains of rice for friction. pour equal amounts of each in and swirl it around for a minute or so. it might make it taste cleaner. if you have a lazy afternoon, some tubing, a glass jar, and a drill, I'm sure you could fashion a bong with your current piece as the bowl end. It's not a complex science.