how 2 block fuel lines ?

I've been working on replacing my engine (82 westy) for a while now, I pick away at it slowly. When I pulled the engine I stuck pencils into the gas lines to keep them from leaking all over the place (aka Muir). When ( a few weeks later) I put the new motor back in I (of course) had to pull the pencils out. I discovered that the pencils had deteriorated. I thought that I got all the junk out - but I believe debris might still be in there. Once it warms up some I'll check it out. I'm looking for an alternative to pencils for blocking the lines. I'm not going to try plastic pens though. It anyone has experience here I'd love to hear about it. cheers john