I pull the oil or B12 in the pin first..then I pull suspension,holding the pin upside down I lay on the edge of the bed and stick the needle in so it is sticking straight up..the the suspension will mix with oil a little but it wont clog the pin..you will notice when it hits the suspension it will start to shoot fast, try to slow it down a little, then the oil will finish through.
Took me a LONG time to figure that little trick out.
God Bless