Ho do you spell words into Google Voice?

Google Voice is generally pretty good at recognising what I’m saying, but if it doesn’t recognise a word, I would have thought that spelling it out should work - but it doesn’t for two reasons.

One is because it puts a space between the letters, and the other is that after I have spelled out three or four letters it guesses (always wrongly) what I am spelling out.

I have (of course) Googled this. The problem seems to go back a long way, and no-one has found a solution.

Is there a way to get the right word in to it?