I know there are some of these published all around the internet and some of them are pretty good. I found most of them to be over engineered or cost more than they should. I just finished the job tonight on my 94 850 wagon's control arms.

Here is what I did and a list of what I used.

1 Foot long 1/2 Carriage bolt and nut to fit it. $1.00
4 Flat washers $.50
1 36mm axle socket - Had it in the tool box.
Simply put use the socket as the receiving end and put the carriage through it with a vice grip on the square end and the washer between then the nut and washer on the other end and straighten out the bushing and crank it down!
Here is a picture of the parts laid out and one of the tool in operation

Hope this helps someone do this job fast and cheaply.