Easier than a 25 gauge surprisingly, your pushing on such a small area the psi is very high. People say to back load the slin pin with a 25 gauge or whatever - no need though. Pull the plunger back on the slin pin balance the tren /test whatever upside down (i use 2 stacks of dvds) and let the slin pin hang upside down. Return 5 mins later to find a slin pin full of lovely oil with 0 bubbles.
30 or 29 gauge and how long?