Having difficult time finding comps.. Am I doing this right?

[Pedro Oliva]

So ive been doing trying to find comps for homes that Ive been randomly selecting or see that are fsbo, in order to practice how I would go about finding deals. I get the address and then use the apps, zillow, realtor.com, trulia, homesnap, and redfin although not available in my area. I do a search for sold homes with similar rooms/bath/sqft on the same street. This usually results in 1 or 2 homes within the last few years if im lucky. Zillow will come up with its 'zestimate' but have been told not to put too much weight into this. The 'zestimate' will also be double the value of sold homes in a different neighborhood, which makes me think that an investor has picked up the sold homes, no clue as to how to find this out for sure though. Im wondering if Im going about this the wrong way on finding comps, or if I should tweak my searches. Also came across the corelogics realquest service, would this service be worth using and be more reliable than the free resources? Thanks for any tips in advance!