KYFlyfisher, you can use Red Dot in 9mm but there are better choices, especially if you want to replicate factory load performance. Red Dot is one of the fastest burning propellants available to handloaders and has a very fast pressure peak if you load up to near or Max. charge level. If you only want to shoot light loads there are still better powders and about the fastest ones I'd use personally would be Ramshot ZIP or W231. They are more stable in high pressure loads. I just don't like to see newer reloaders using Red Dot in high pressure cartridges. On the other hand, HS-6 will easily allow you to produce factory load level velocity. I'd also recommend that you get some more reloading manuals. I'm not partial to the from LEE. Add a Lyman 49th edition or the Lyman Pistol & Revolver III. Or better yet, get both.
In .357 Magnum, there are better powders than HS-6, but since you have it you can use it. You just won't be able to produce velocities as high as what slower burning are capable of. For lighter JHP or cast lead loads it will work fine as well as in .38 Special but you'll need to use a small pistol magnum primer to reliably ignite it. I would stay away from Red Dot with the .38 Special or the .357 Magnum since you're just starting out. You could accidentally double-charge or even triple charge a case. Naturally you should pay very close attention when you are charging cases, but Red Dot adds an unnecessary risk. Use the HS-6 with a small pistol magnum primer since you already have HS-6.
For 9mm, .38 Sp. and .357 Magnum data go here: Cartridge Loads - Hodgdon Reloading Data Center - data.hodgdon.com
They use a different bullet but you can still use the data because you always want to begin with a Start Charge and gradually work up from there as stated in the load manuals.