Preflop

The ProPokerTools x% hand ranking is a good place to start. For a 20% UTG open in 6-max, you can write 20%6h. 

Postflop

With the preflop ranges chosen, use filters in PPT to select hands for his various ranges postflop. 

For example:

Villain raises a 20%'ish range from UTG (you can find the open% by position from the HUD), you call on the BTN. The flop comes Ah Ks 2d. If you want to know how often he has top pair or better, here's the PPT input:

20%6h:(AA,KK,22,AK,A2,K2,A)

This can be written simpler. "A" covers all possible hands with an A (top pair, top + bottom pair, top two pair, top set), so we can shorten it to:

20%6h:(A,KK,22,K2)

But it's fine to write the long form to keep it organized and easier to interpret quickly.

Another thing  to help range is to plug some hands into the rank function on PPT.  While this is not gospel for starting ranges, it gives you an idea of where hands fit into rankings.  For example this is the ranking for all JJ hands that contain one pair.  

You can get more specific and see how specific hands fit into the percentage of hands and this can help you get a feel for the range of hands that people are likely playing.  Nothing will ever beat getting more specific reads from hands at SD.  If villain shows a really trashy QQ hand from UTG but is playing a tight range we can assume that his 20% of hands might be very OP heavy and we can start to range him even better than just saying 20% of hands.