Here's an extract of the procedure I follow, by John Snyder.
1--clean and sterilze several mason jars,or large beer bottles and lids
2--take some of your wort as it reaches the end of the boil
,just prior to adding the finishing hops,and transfer the needed amount of the boiling wort to the jar,or bottle(empty the hot water first)and cap immediately.Let the wort cool to under 90 degree F and then refrigerate until your batch is ready for bottling
3---At bottling time,boil the saved wort for 10 mins.and chill,then add to the fermented beer and bottle.It is important to use the proper amount of unfermented wort for the particular beer you are priming
HERE IS A ROUGH GUIDELINE:based on 5 gallon batches.
Original gravity reading: Amount of unfermented wort:
1.030 2 quarts
1.040 1 1/2 quarts
1.050 1 1/4 quarts
1.060 1 quart
1.070 3 1/2 cups
1.080 3 cups
1.090 2 2/3 cups
1.100 2 1/2 cups
This should accomplish the type of priming you want to do.
Priming is not necessary in a true krausening,but is complicated.The home process that is outlined above should serve you well.