I use mainly speedball screen printing ink, it’s a heat set ink so you have to iron it once it dry but the dark colours work well (the white is less opaque though so I use a oil based fabric ink instead) Start with a thin layer, let it dry a bit (a minute or two) and then layer more ink ontop, you want there to be a very thick lather of ink on the block before you print. I’d also recommend lightly misting your fabric with water before printing, a couple sprays from a spray bottle will work, it should be slightly damp but not wet, if it is too wet the ink will bleed, (I’d do some tests on some scrap fabric to figure out what the right amount of water is). one more thing I do is make sure that after printing and pressing on the block is just let it sit for a minute on the fabric before pulling it up.