Well usually it's to make custom colors (kinda useless now with the range offered by import brands) but I guess you could try to get more pressure in, but often it doesn't work too well. you can use the WD40 tips but the tube is small and it will take alot of time to fill a can and is just lots of hassle. I prefer to do it this way.... Get a bic pen, a razor or sharp knife and a fatcap for reference (any kind that works on the type of cans you wish to use). Breakopen the pen and take the tube that contains the ink. Cut off about 1 1/2" of the end of it (part with no ink, or clean out the ink). So now you got yourself a nice fat tube for a much quicker paint transfer. On both ends of the tube cut little notches. Use your fat cap as a reference. Look at the notch on the stem of the cap, cut one on each end of the tube of a similar size. Better small then big, small will mean less speed but at least it won't spurt all over. Now put the can you want to fill with paint in the freezer. Not recommended to try to add paint to a full can lol.... Leave it there bout 15-20 minutes, cans freeze very quickly. Get some tap water in a large bowl, as hot as it will get. You can try using heated water on stovetop or someshit, but go too hot and boum. yeah. Put the donor can in the bowl of hot water for 10-15 minutes (keep the water hot) When all this is ready stick the tube into the cold can as if it was a cap. This can will be at the bottom to help the transfer. turn the hot can upside down and stick it unto the tube. I really recommend doing this in a plastic bag or outside, sometimes it kinda explodes paint all over lol. Then just press the 2 cans together and paint will go from hot (highpressure) to cold can (low), hold them together untill you stop hearing paint transfer at a high rate, that means the pressure in both cans is near equal... if it hits equal you got a mess on your hands haha. reheat and/or freeze cans to continue untill you feel the can is full.