Steam blocking acrylic is permanent unlike blocking wool. Steam melts the acrylic into place and it stays in the new position which is why it "kills" it, no more bounce. Real hair takes a lot of training to stay in place. My wool items need reblocked every time I wash them, just like my hair did when I had hair.
If you're just trying to soften and even out the stitches washing and drying should work.
If you need to stretch it into shape then you'll need steam. I bought a steamer for that reason, they don't have to be expensive.
I can't comment on Suzeeq's method other than to emphasize not to press, even my steam head pressing a little can look pretty wrong.