My best advice is to have your machine on a large table that can help hold the weight. If you can then move your machine to the left/right depending on which border/edge you are working on. If you can't move (set in table machine), I sometimes position extra chairs on the side I need to hold the weight.
Then I use my hand to help hold that side (I try to position the edge so most of the quilt is to the left of my domestic). That said, I now have a sitdown HQSweet 16 that has the same amount of table space on both sides and sometimes I still use a chair for Q and K sized quilts, but generally still try to keep the bulk to my left ( I am right handed).
Your goal is to have something else support the bulk and use your hands to move the fabric near you without too much tension from the bulk.
Good luck and realize that the more you practice the better you will get! Don't sweat the small stuff!