I did it for my buddy last week and I'll be doing it to my new to me '05 DR650 that I pick up tommorow.
I have a 1/2" x 1/2" x 20" piece of square steel rod that I tapered on one end and it works great. Sure you could buy the Suzuki special tool but mine works on any damper rod type fork and yours could too.
I've also made one by grinding down a 1/2" drive impact extension. Just use a damaged or cheapie 1/2" drive impact extension and grind the part that goes into the socket down to a tapered end. I've heard of people using broomsticks but I've never tried it myself. Easy and cheap enough to try if you dont have any other materials available.
Loosen the top fork cap before you remove it in case you dont have a vise.
Remove the fork leg from bike, then try to loosen the bolt (8mm allen) on the very bottom of the fork. This bolt holds the damper rod in place. It might come loose with the tension of the fork spring holding the damper rod but dont count on it, there isnt very much tension in these forks.
If the lower bolt just spins & spins but doesnt start coming out, then remove the upper fork cap, preload spacer, washer, then fork spring. Lay those to the side on a clean surface then dump out the fork oil. Now it's time to stick whatever tool you fabricated down the fork tube into the damper rod and your tool will hold it in place while you remove the 8mm damper rod screw. Pretty easy.
Now if you're going to lower the front, slide the top out spring off the damper rod. Take the preload spacer you remover earlier from the top and slide it onto the damper rod. Now put the top out spring back onto the damper rod. Insert your fabricated tool into the damper rod and slide it back into the fork. Attach & tighten the damper rod, then fill your forks with fork oil.
I used ATF and filled it 5 & 1/2" from the top of the tube with the fork fully collasped. This was purely experimental and works great according to my buddy who owns the DR I'm talking about. Use whatever oil you prefer, and what fork oil height suits you.
Extend the fork, drop the spring in, then the washer & cap it off. Done. Now you get to do it to the other side.
Note: you can add another preload spacer, or washers for additional preload if you wish. I added 3 flat washers I had laying around. That was maybe a 1/4" of additional preload.
My buddy says the front feels great, and it made the soft rear that much more noticeable.
Lowering the rear is easy enough, choose the bottom bolt hole on the lower shock mount. If it's not low enough, remove the shock, remove all the preload from the shock spring, remove the spring, then remove and flip the shock spring seat and this will provide you with the complete Suzuki lowering option.
Dont forget, you're going to need a shorter kickstand. I cut 2" of it and had it welded back up. Works great.