After removing the old bushings, thoroughly clean the inside of the trailing arms.
1) Install the THIN bushings on the INNER side of the trailing arms by hand. Use a mallet to install the bushing the rest of the way.
2) Install the THICK bushings on the OUTER side of the trailing arms by hand. Use a mallet after.
3) Lubricate the grooves on the races with lithium grease. Start installing them inside the bushings by hand and finish it off with a mallet.
Remember: Thinner on the inner, thicker on the outer.