I use Isopropyl Alcohol (99.5% v/v) on al my ep's barlows and filter when needed,
along with 100% natural (scent free) cotton buds and balls. Works a treat mirror
finish everytime. But there is a lil bit of a knack to it, and some ep's are easier than
other. IE: my pentax xw's are a far easier to clean than my 30mm SV, due to the
fact that the top section of the eyeguard is easily removed.

I start from the centre and work out, changing the cotton bud or ball with every
wipe. I also use the moisture in my breath along with the Isopropyl Alcohol in the initial wipes.

I brought a 500ml bottle from a chemist in town for $30.00 from memory. I half filled
one of those eye dropper bottles and have cleaned my ep's several times and still have
close to half a eyedropper bottle full. One word of warning when I cleaned my
Meade #140 apo x2 barlow. Just the fumes are enough to damage the high quality
and durable printing that is so easily removed. I have never had this problem with
Vixen, Uni Optics, Pentax or Astronomiks.

Al Nagler has a good dscription on cleaning ep's
http://www.televue.com/engine/page.asp?ID=143

regards,CS