Using ND filters

Hello all, and Happy Easter! I've been reading up on a few techniques for long-exposure photography, and thought this would be useful to a few people: http://www.mattk.com/2013/02/11/long-exposure-light-leak-with-my-lee-big-stopper/

It's talking about the Lee Big Stopper specifically, but all that is, is a 10 stop ND filter (of really good quality, apparently). I didn't realise that when you do long exposures (really long) that covering the eyepiece was so important - good to know in advance! I've got some cheap stackable ND filters I'd like to try out soon, so I'll have to remember this and bring something to cover the eyepiece with.

(image from John Birch Photography)