Wash the thing in hot water. Add the powder not necessarily, unless of course a thing is not contaminated. The former tissue can be boiled, so the effect will be much better. But colored can lose brightness.
Taking out a thing of hot water, quickly place it in ice. Can add crushed ice. If rapid change in temperature of the tissue decreases. Usually the width remains the same, but the length shortened a few inches.
Press on high speed centrifuge. If you wash in the washing machine, put 1500 rpm. The more spin, the greater the chance that you will achieve the desired result.
Hang the thing to dry on top of a radiator. Don't forget under the fabric to enclose any a towel to avoid yellow spots. After a few hours you will be able to evaluate the result. If a thing is deformed - do not worry, because it still did not fit you in size.