Major difference even with a the Rattle Can. Recommendation time:
Start out where you are right now, sand the repaired areas down to the glass, add some filler, B***o will work, but I do not like it. Duraglass is the better because it has fibers in the filler, if you can find a pint or quart go for it. Now sand it, if you sand it just before it hardens, called the green stage, you can get it to a rough shape without major sanding. Once set, sand out to 220 then apply a thin layer of glazing or spot putty (bondo brand is good - red tube). Let set, usually pretty quick, sand out with 220 or 320 then use the filler primer. This method with get you an awesome finish. When you get ready to paint - wet sand the primer with 320, paint, let cure, wet sand 320 or 400, spray another coat, let cure and admire - if needed spray on a clear coat. That should do it, take your time and you will get a great looking finish, remember 90% of a great paint job is in the preparation of the sub layers.
Now that you have an awesome visor, get ready to paint your truck - LOL - J/K. Good Luck - if you have any questions ask here or PM me - not an expert, just have done quite a bit of FG work and body work on my custom 95 . . .