So I tried to triangulate the position of several different SAM positions using the RWR and I found that it was pretty accurate. You could probably do it several ways, but the method I used was:
1. When I first get painted by radar, fly so it lines up with a tick on the RWR. Usually I'd beam it or put it 135 degrees back (45 degrees back from beam). Also I guess you could fly straight away. It doesn't matter as long as the letter/number in the RWR symbol lines up exactly with a tick on RWR (don't fly right at it and get shot down).
2. Then I just find the same tick around the HSI and note the bearing, while at the same time hitting the "Mk" (create overhead mark point) button on the UFC. (lets call this Mark A)
3. On the CDU, I then created an new offset from that markpoint about 100 miles in the direction of the SAM (from the HSI). This will be called MSN0xx. (for this example lets call it MSN006)
4. Next, I flew around the SAM until I got painted from a different angle, and again noted the exact bearing by comparing the RWR to the HSI, and I created a markpoint at that spot. (Mark B)
5. Created another offset from the second markpoint in the second direction for about 100 miles. (MSN007)
6. Built a flightplan using the following waypoints: A, MSN006, B, MSN007.
7. There should be lines connecting all your waypoints on the TAD now. In the center the two big lines should cross. This is where the SAM is.
8. Placed a markpoint where the lines crossed on TAD (TMS right short, Mark C).
9. Added Mark C to flightplan and slewed TGP to steerpoint (or set Mark C as SPI and slave all to SPI).
10. Find SAM (usually it was pretty darn close to Mark C).
So I dunno if this is helpful to anyone, or if anyone has a better (faster) way to implement this idea. Also, I was curious if anyone knows if this is ever done IRL? (maybe in a different aircraft with a better RWR and a computer thats set up for it?) Anyway, I found this to be pretty useful for finding SAMs if you don't have any SEAD to call in and you can't get the SAM position from your wingman's superhuman vision.