My preferred method is to SOAK your blanks in your first color. No vacuum at all. You will have to play with the amount of soak time. When you are satisfied, cure your blanks in the oven. After they are cured and cooled down, run them through the vacuum chamber with your second color for the full time until the bubbles stop. The soak color will penetrate the softer, more porous areas of the wood through natural capillary action but not saturate the wood. Then, when it is cured, it becomes impervious. The vacuum will pull the second color into the parts of the wood that did not achieve saturation from the soak and you will end up with a blank with 3 or more colors. Which color to do first?...the first color will be your highlights while the second color will be the predominate color of the blank.
Hope that helps some. If you need anything else, please don't hesitate to let me know! I am here to share anything I have learned along the way and support you in any way I can!