Reddit mentions of Woodstock D3292 Drum Sanding Kit, 16-Piece

I either use these:

https://www.amazon.com/Woodstock-D3292-Drum-Sanding-16-Piece/dp/B001XQMRH4/ref=br_lf_m_bv4y9v7p5tba8wp_ttl?_encoding=UTF8&s=hi

Or:

https://www.amazon.com/Black-Hawk-Mounted-Wheels-Aluminum/dp/B01MDQW98P/ref=mp_s_a_1_11?ie=UTF8&qid=1539429033&sr=1-11&pi=AC_SX236_SY340_QL65&keywords=flap+wheel+sander&dpPl=1&dpID=41vmTZGsF0L&ref=plSrch

Of the correct size. I put them on a drill press or they can be used in a drill

You should be able to get these at your local hardware store for pretty cheap. http://www.amazon.com/gp/aw/d/B001XQMRH4/ref=pd_aw_sims_1?pi=SL500_SR115%2C115&refRID=082YF0H44WVZT0N8EWN7

Invest in some drill drum sander parts like this:

https://www.amazon.com/gp/product/B001XQMRH4/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Mount your drill in a vise (if you don't have a press) and it will make your sanding effort a lot easier in those hard to reach places.

You can probably use a dremel, but things like a flap disk or belt sander would remove material faster. If you already have a drill press and want to save money, you can get these which are inexpensive, but for ~$10-$15 more, you can get an angle grinder and flap disk.

This website has a lot of handle materials and spacers. But there are plenty of other websites, too. Plus I don't know if they ship outside the U.S.

You mentioned a router... How about getting a router with a variable speed motor and chucking up a 1/4" shank sanding drum? You will have decent control over the grit and you'll be able to easily guide the router around the curves.

http://www.amazon.com/Woodstock-D3292-Drum-Sanding-16-Piece/dp/B001XQMRH4/

McMaster has a good selection of sanding sleeves.

I ordered these a little while ago...not as long as the ones in the video but for $11.40 you can't go wrong.

http://www.amazon.ca/Woodstock-D3292-Drum-Sanding-16-Piece/dp/B001XQMRH4/ref=sr_1_2?ie=UTF8&qid=1420558539&sr=8-2&keywords=drum+sander+kit

Maybe take a drill, place it in a vise, the use a drum sanding drill bit like these? https://www.amazon.com/Woodstock-D3292-Drum-Sanding-16-Piece/dp/B001XQMRH4/ref=br_lf_m_bv4y9v7p5tba8wp_ttl?_encoding=UTF8&s=hi