If I'm sure the questions are not duplicates then I have no problem with copy/paste answers, however I try to always link to the source answer at the top of the question so the user can read it and possibly other answers there that might relate to them too.
Usually what ends up happening is I prefix my answer with a summary of the solution, add a link to the 2nd answer to say where I got the answer from, then copy/paste the 2nd answer in block quotes
Everyone once in a while when the answer is similar, but not exact, I'll just copy/paste the answer straight and modify it to fit the 2nd question, however I usually still leave a link to the original answer for further reading if the other answers there may apply too.
However like Chris said, be sure it's not a duplicate first. If it is a duplicate, you don't want to copy/paste answers because its likely the questions will become merged, and you'll have two answers saying basically the same thing. So vote to close as a duplicate instead if the questions are the same.