The foaminess indicates that it needs additional refrigrerant. You can get the refrigerant to flow faster out of the can by placing it in a hot water container. Make sure the can is upright and that you are on the low side. I would suggest picking up a inexpensive gauge from auto zone that will tell you if you have enough. I picked up one for 14.00 and hooks up to the low side and is color coded and very easy to use.
Good luck
Armind