In , David B. suggested:

https://www.youtube.com/watch?v=BP2ffBSD2A0

Nice link! Since I watched it, I'll summrize for those who didn't.

1 Paint can
2 Drill two 1/2-inch holes in the lid
3 Screw in male-threaded quick-connect for air hoses
4 RTV them or put a nut to prevent air leaks
5 3/8-inch tubing on the quick connect
6 Regulate air compressor to 2 to 5 psi to test for leaks
7 Wet half a rag with baby oil & place in the paint can
8 Light the top of the rag and cap the paint can
9 INLET is 2psi from the air compressor
10 OUTLET is 3/8-inch vinyl tubing filling with smoke

Then on the vehicle
11 Pull off the power brake vacuum hose from the manifold
12 Remove throttle body tube & block the throttle body
13 Connect to intake manifold where the brake booster went
14 Look for smoke!

The theory is that the fire can be kept going with the air coming in from
the compressor and the air pressure of 2psi will push the smoke through the
vehicle plumbing.

The caution is that most air compressors don't have a regulator that can go
that low reliably, and you don't want too much psi or you cause leaks.

I wonder if a diesel glow plug and hookup to the car battery will be better
for generating the smoke from the rag soaked in baby oil (he said mineral
oil is the same thing I think).