Gymschu, with all due respect, you have me confused. You're telling Karen to use two different primers. Karen, spot prime the knots with Zinsser BIN, a white pigmented shellac. Then touch up with the finish. Just out of curiosity, how long did take for the knots to burn through?You need to prime with Cover Stain oil base from Zinsser or oil-based KILZ...............basically, you need pigmented shellac as a primer. Any water-based primer is going to draw out the tannins/oils in the wood. The shellac seals out the tannins.
Sorry about the confusion..............just be sure to use what Chris and Joe have pointed out. I have so many cans of primer laying around that I just grab what I know works........I don't always remember (I'm old) exactly.......I still get B-I-N and Kilz mixed up.......anyway a white pigmented shellac will seal out those knots and give a good surface for applying a finish coat or two......nuff said.