If you pitch cool, and let it rise to your target temp, then in theory you shouldn't realty need a d rest. I, like most I think do it anyway. When to do it isn't realty an exact science. I think Jamil Z recommends raising the temp for the last third of fermentation, but it's not like the yeast dies once it reaches terminal gravity, so I'd imagine it'd still work even if you waited until then.
What I do is pitch at 45, and raise the temp 1 degree every morning and night until 50 for most of my lagers. When fermentation noticeably slows I raise they temp to 58, and let it sit for a week or so.
Edit... Then I keg and lager. I don't use a secondary for lagering.