A D dorian scale would sound best when applied over a D- chord, but when you are soloing you are not playing scales up & down, you are creating melodies, so trying to match up each mode with the chords flying by will drive you crazy. Not to mention you are going to be spending more energy trying to figure out which mode your in then you are on creative thinking. Here's some tips, I hope you find them usefull;

1) when soloing over a diatonic progression think the major scale that the chords relate to
2) the strongest note you can play over a chord is another chord tone

lets use your 1 6 2 5 prog as an ex.(C A- D- G)

C & A- are closely related, so I would first get use to improvising in the C maj scale phrasing around the notes c,e,&g
D- & G are closely related (they both have a tonic resolution to the 1 chord )so for the 2nd part of that progression I would phrase to the gbd&f

so I've now just narrowed down that 4 chord progression to two parts, playing the 7 notes of the diatonic scale and phrasing to the notes that will be reflected by the passing harmony

This is only 1 way of looking at things, the possabilities are endless, but this is a good way to start. Remember, don't over intellectualize, let your ear have the final say.

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