Without anymore detail than provided there are several options to achieve the "distressed look" as I will go through several options. Most screenprinters in the past have actually distressed their positives first and this entails the following:
1. Scratching or beating positives with chains (quite Neanderthal but it does provide a custom look)
2. Tinting your art with a distressed screen
Now concerning your ink choices, soft-hand additive is chock full of plastisizers and adding 99% will not give you any softer hand. It will however totally destroy the intensity of color so here are several options.
1. Use a "curable reducer" note the word CURABLE, this is a body reducer that can make the ink have the same characteristics as warm syrup, very runny and it will permeate the fabric.
2. When using soft-hand and especially a curable reducer you'll want to go to a much higher mesh count, nothing lower than a 195 and upwards to a 250 mesh count. This coupled along with an ink that has been reduced using a curable reducer will "dye" the fabric versus just laying it on top. A sharp squeegee, 70 duro plus is recommended, for more saturation you can use a softer squeegee but your last screen should use a hard, sharp duro to drive the colors further into the fabric.
3. Use a halftone tint over your entire design, say starting at a 70% tint. Not my favorite way to reduce hand but your only laying down 70% of the ink.