Man, you are doing just fine, the forumites here are going to love you cause you have made a great effort to do a bunch of research on your own! Also Tack Cloth FTW!!! Never heard of that before but I am sure as heck going to be getting my hands on some. I found this DIY Tack Cloth article: http://joneakes.com/jons-fixit-database/1137-How-to-make-a-tack-cloth
, but I think i am going to try out the real thing first.
On to your questsions, personally I would let the box cure longer between your first and second medium color coats (24 hours if I can be that patient, usually more like 4-6). I would only sand the color if you notice any roughness or bits or whatever.
Also I only tape the bottom edge and the screw holes. I have had bad luck when covering the holes completely from the inside, it has caused drips from paint building up on the tape, and more work to clear out the drill holes afterwards. I have tryed taping just around the internal ledges/edges of the holes (not closing off the hole entirely) and that seems to work well too. If you do not do this, you will want to make sure that you clear out any paint in the hole after it is well dry to ensure that your jacks are going to ground out well against the enclosure. I just use a hobby knife for this.
For lettering, I use Water Slide paper decals, the clear kind, which work great for non color images and text. I know others use paint pens and write stuff on by hand. There are also a couple of decaling systems out there like Pulsar Decal Pro. Some just use letter stickers like from a craft store. To do color decals some people use the white Waterslide decals, others use printable vinyl decals. There has been some amazing etching stuff coming out on the forum here lately as well.
Then clear coating over top of whatever lettering you do to protect it. Lots of people use spray on clear coats, and if you search spray clear you will get some good stuff. I have been using envirotex, which is a 2 part pour on epoxy, which give a really glossy thick finish and is really protective (but a total PITA to use).
Hopfully that gets you started. Post any more questions, there are lots of super knowledgable people here.
Be careful not to order the dysfunction tube. Those tend to whine a lot and blow up.