I am at present rigorously studying 擬音語／擬態語 (an entire world of its own!).
The definition my book has for ぼちぼち (also ぼつぼつ) is:
1. Gradually; slowly but steadily 2. Used to describe something that is about to happen. Imminently. Right away. 3. The condition of many dots or other small objects scattered around.
Ignoring definition 3, definition 1 seems nearly identical to どんどん and だんだん:
ぼちぼち ←→ どんどん ←→ だんだん
and definition 2 seems nearly identical to そろそろ:
ぼちぼち ←→ そろそろ
Is this correct?? If so, are they freely interchangeable in a given situation, etc.? Can someone explain any nuances amongst them??