I am going to apply some anti noise stuff to the back of my brake pads, and from my understanding it just goes on the entire back of the pad. Is this ok to get it on the piston, it seems impossible not to...? Also, are you suppose to apply it to both brake pads?

Nevermind.....I just bought some shims instead

The advice is good from the others, put the silicone grease on all pad back and shim surfaces, and only needs to be onn the areas of contact with the piston. I like to use enough to get the piston liberally coated on the contact surface with the shim.
Also the best grease I've used is Dow-Corning Stopcock grease. This is much more viscous silicone than what you get from an auto parts shop, and stays in place better, and has better heat stability. You can get it from a chemical supply catalog like Fisher Scientific or McAlister-Bicknell. This stuff is also great to put on exhaust pipes when putting in a muffler so disassembly is a breeze years later.
Stay away from that red 'goo' from Permatex. It hardens like glue after a few days and gets brittle and can chip off, making the application pretty useless after a while.
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'89 245 Sportwagon, '96 960 sedan

Use good anti-noise stuff - I use a silicone gel with molybdenum disulfide, they gave me a free brush and the stuff does not migrate to cause trouble. Ensure that your calipers are properly lubricated with fresh brake fluid, then use a visible film of brake caliper lube on all pins and other contact surfaces (yes, even ss shims coated with nylon, etc.). Don't worry about the stray dab on the pistons' outer edges, just make sure the grooves on the clips on either Girling or ATE calipers in which the pads slide are in place and properly lubricated. Your brakes should be fairly quiet and stop you in an awesomely short distance in a Volvo!
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(1990 244DL @ 156K, daily driver; 1994 850 ti+ @ 122K, current project: 1995 Fordillac Exploder Eddie Bowel Edition Wifemobile@123K; and mein bruder's Chevy trucks, etc.);)

Just did the pads and rotors on the 242 a couple of weeks ago. I used Syl-Glyd from IPD and coated all the hardware, both sides of the shims and the backs of the pads. There is absolutely no noise from these brakes (Ate Power Discs and PBR Ceramics).

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don hodgdon '89 744ti, '81 242t, '71 D-35...just waitin' for the glue to dry :-)