2oz per gal lambic for ~ 5 vol CO2 & .5 - .75oz per gal flanders for ~ 2 - 2.5 vol CO2.
the only way to know how much carbonation you'll have is to know what your FG is and how long it's been where it is. if it's 1.015 and has been steadily dropping for 1 yr, it may still drop adding to inaccurate carbonation rates. if it's 1.004 and steady, i'm thinking that's optimal that way you can be positive how much additionally added sugar will affect end product (ie: carbonation).
i bottled some flanders red yesterday using champagne bottles and regular wine corks & cages. it worked out great, but i'll let you know in a year how it stands the test of time. i used around 2 oz for 2 gal and added a few sprinkles of wine yeast for carbonation. beer was 1.004 when i bottled btw.
http://www.homebrewtalk.com/f35/corking-your-belgian-bottles-portuguese-corker-137529/