In Japan I often have to call somewhere and explain my name such that the person on the other end can write it down. My name is "Sepponen Bemmu", which I want them to write down as "セッポネン・ベンム".
Is there a way to "spell" katakana verbally?
Generally you just read out the individual kana, and for little-tsu you can say
小さい「つ」. If you want to specify it's katakana, you can say
If there is some confusion you can say the "group" of kana it's in, then say
の then whatever one it is specifically. So for
か you would say
か、き、く、け、こ、の「か」. With any luck that is how you learned them, so it shouldn't be too hard to get the hang of.
For separating your first and last names I'm not sure if the person you're speaking with will realize they're separate, so you would add in
そうして, or something similar, in between.
So, if you wanted to spell your name it would be something along the lines of this:
かたかなで、セ、 小さいツ、 ポ、 ネ、 ン、 そうして ベ、 ン、 ム
At least, that is how I would do it.
I realize it's a bit difficult to understand without hearing it, but hopefully I explained myself clearly...