Here is D major with every double stop played with the 2nd and 4th fingers.
This is particularly useful since the 4th finger is often quite flat in 3rd and 4th positions.
The intervals are always the same for each type of scale. Calling them out loud before playing the scale helps you remember the sequence. For the major scale in 3rds it is:
major, minor , minor, major, major, minor, minor, major.
You can also play a version of the game of hopscotch on the studio floor calling out the change of interval (close, far, far, close, close, far, far, close) as you jump with feet together or feet apart.
Scores - Double-Stop Scales - Same fingers - violin & viola