Your kit looks great so far. Keep us updated, please!
Best moves I made was to get a set of Formations tools and the ET Model PE set for the DML 1C Firefly. The tools are superb and really dress up the exterior. The PE is very good- and cheap!- giving you a ton of useful parts like Periscope guards, alidade sight, sandskirt strips, fenders, as well as tool straps and clasps, light guards and track skids. ( I had already thinned the DML skids and drilled out the holes before the PE arrived so I'll use them on another vehicle.) The Tasca Firefly VC come with separate backs for the idlers which fit the DML idlers perfectly- I cast up a couple of copies to fix the DML's.
The other very useful addition is a set of the Archer casting marks. I added some to mantlet, turret, open hatch, etc.
Not knowing much about the 1C I found Phil Dyers article on detailing this kit in the old Military Modelling Special of April 2001 very useful.
Keep up the good work... Now to finish mine in time for a show this weekend!