Gone are the days of corners taking ages to do, I use a Bosch Nose sander, I have a fein and Festool detail sander, but rarely use those nowadays, these days i favour the nose sander and or my trusty Tungsten scraper!

There is a stanley version which is available from B&Q in the UK and also the Linbide version is equally as good. see the limbide version at http://www.linbide.com/product.php?sid=438&cat_id=23

It removes old varnish and Bitchumin in seconds, apply pressure and scrape from right to left, then left to right then finally with the grain, sand by hand or with a detail sander with the grain at 60grit, 80grit and 120grit then your done, lovely corners achieved easily and no outlay to hire a decent corner sander. I always scrape my corners first, it saves on sandpaper no end.

The scraper is great at getting into awkward places and behind radiator pipes, with no risk of damage to the piping.

They cost about £10 UK and the blades stay sharp for ages.

Also great for dry scraping bull noses and stair Kicks before sanding.