You've got lots of good information here for washing your quilt. The first thing I would do is dampen a white paper towel and rub a little spot in the center of a dark fabric. Choose a non visible spot near the edge. After rubbing, check the paper towel for colour transfer. If you have a lot of colour on the towel you know it is going to bleed. If you have a lot of really dark fabrics and really light fabrics then you will need to be careful. I do as other have said, fill my top loader with a lot of cool water, submerge the quilt with color catchers and hand agitate for a few minutes. I then spin in the washing machine. If after checking for bleeds it is clear I put it into the dryer for a bit. I take it out before completely dry and block it.
You can wash with Synthrapol but it needs a slightly different procedure. Synthrapol keeps loose dye suspended in the wash water instead of depositing on other fabric. Good luck.