Personally I use a LED Lenser P14 it's small, light and has a beam you can reasonable focus which is important for accuracy when light painting, also for larger scenes you wish to paint it also puts out enough light to be able to cast its light a decent distance...it also takes AAs which of course your likely to already use plenty of handy for saving money on rechargeables...you can now get this from about £40
I've also recently started using a LED Lenser P7QC this is actually a brilliant bit of kit for light painting as aswell as the standard white beam it also is able to do Red, Green and Blue light...and once you get used to it it's possible to semi mix those colours in light painting to create slightly different tones/colours...the main disadvantage of this model is however it's not focusable like the P14 and it's also nowhere near as powerful, but it's still a nightly useful but of kit, it also however takes AAA's which is a shame...this however is a more expensive torch coming in at around £65
Edit: seems while I was typing you edited your post which I didn't notice, really what your describing is more what I'd consider light graffiti rather than light painting, and while both optioned I've mentioned would still work, they're a bit high end for what you need really...really all you need is a simple on off torch that's quite low in power, I see mention of a candle style, personally I'd not go for that as sometimes when I do light graffiti I like to cover the light source with my hand to create a pause/break in the graffiti...
Matt