I use the new type solder that plumbers use for non-leadhousehold plumbing. It's made by Oatey and you can get a lifetime supply 1/2 pound roll at your local home improvement store for about 5 bucks.

I use the soldering flux used with Sta-Brite silver solder. They have an 8 ounce refill bottle, also about 5 bucks from your hobby dealer.

Be sure to clean off the flux after soldering. A paper towel moistened with alcohol works well, and then wipe on a little oil to keep it corrosion free.

4-40 rods and clevises need only a 100 watt gun to heat thoroughly. A torch will take the temper out of the clevises.