Like you I have thankfully completed the Azed today.
In doing the Mephisto and Azed we are regularly challenged by obscure Scottish words, plus those from regional dialects and archaic/Spenserian origin. They can be looked up in Chambers but only once the word is known.
It would be good to have a Scottish thesaurus so we could look up the English equivalent. Taking AZED 1928 as an example, it would be good to look up 'firework' for 11a. The only solution I know is the DSL or Dictionary of the Scots Language - refer to http://www.dsl.ac.uk/dsl/
Unfortunately, a DSL search on 'firework' leads to lots of words but not the right one. Annoyingly, a search on the correct solution shows it to be present in the DSL ! It is probably better than nothing though...