Carbing just a couple beers?

I keg everything I brew now but would still like to be able to enter my beers in competitions. Unfortunately my kegs don't have a bleed valve so bottling from the keg would be very difficult I would think.

I am thinking about brewing a gallon more each time and just bottling 4-6 beers but was wondering if there is a formula to go by for carbing such a small amount of beer? I've seen the tablets but have many mixed reviews.

1/2 teaspoon of dextrose for 12oz should carb your beers, I've never used the tablets so can't say anything about those, sometimes you have to be quick on the capping. If you have a picnic tap on your keg, you can simply connect a bottling wand to the end of it (The small ones fit in the end of the picnic tap perfectly) and bottle from there and then cap.

when kegging I bottle about a 12 pack with the coopers carb tabs and the reset into the keg - works every time and I don't have to worry about measuring dextrose or corn sugar... 1 tab for 12oz and 2 tabs for 22oz