take it apart and check the siphon orifice behind the tip.
now you have to build a trap door at the bottem to drain the sand to change it
Too bad I don't have a pic of the one I built out of melamine board a few years ago. It has a light, an evac system, a drain/sifter, mesh to put parts on, a plexiglass viewing window, hand cutouts with rubber gloves, a lower shelf for supplies and bucket and it all rolls on casters. Big enough to put a rear end in. Too bad my crappy pressure blaster couldn't keep up.
Total cost around $200 + about 3/4 of a day's work.
Thanks for all the help guys. I am going to try to mess with it a little this afternoon. It is barely 20 out & the garage takes a while to heat up. I have had good luck at HF with returning things but they are not very close. I will see what happens with no tip & the other supplied tips later. I like to call it my "just the tip" game! I had to say it. lol
Stack all the parts in the cabinet in a pile if you can. The "blow by" will do some of the blasting for you on the parts you aren't working on just then, and it'll save time and wear/tear on your compressor.
Use lots of duct tape on the machined area of the spindles -- you don't want to blast those. You can use rubbing alcohol to remove the tape goo and then use some crocus cloth on the spindles to really clean and shine them up without removing any metal material.
Either of your medias will be fine for the aluminum dust shields. Glass bead is used if you want to achieve a "soft" finish on your metal. Since a soft finish is the last thing I need for my powders to adhere, I use Black Beauty slag for almost everything.
Can't help you out with the tip question. I only use one size. :-D
Have fun and be careful!