Here's how I've been stripping painted trim...
Early on when we bought the house, we made the lucky decision to invest in the Silent Paint Remover. While an expensive investment up front, the SPR has saved us lots of cash over the course of our renovation. Specifically, it's allowed us to do lots of stripping work without purchasing any chemicals.
Most recently, we've been stripping the window and doorway trim for our second floor. In those rooms, the original trim has been preserved but painted several times. Our goal was to strip the paint and original shellac off, and then restain the woodwork to match the original look.
For our work on the second floor, we've removed all the trim because the walls all had to come down anyway. That said, these steps should work when leaving the trim in place, too.
First, I removed the paint with a single pass of the Silent Paint Remover. Applying the SPR for 10-15 seconds to any 20"x5" area should blister the paint, as shown in this photo. (Note: Be careful to not let the SPR stay too long or you'll burn the original wood surface1)
While still hot, take a quick pass with a wide flat scraping blade. Typically, the paint should come off easily. This is especially true when the paint was applied over a smooth surface like varnish or shellac (like this example).
After a single scrape, you may find that scraping a second time is complicated by residue left on the blade. Latex paints may become very sticky when hot and stick to the blade.
To address this, I keep a second, narrow blade handy to scrape off the primary blade between each pass. It may also help to apply the SPR a second time for about 5 seconds between each pass.
As a second step, after going over the entire board with the SPR, I then go over it again by rubbing it down with denatured alcohol. I apply the alcohol with steel wool.
The alcohol degrades the shellac, leaving the warm smooth stain beneath. The nice thing is that the process also loosens any remaining paint residue because the alcohol is loosening the shellac below. I find that often a pass with a paper towel is necessary at this point to remove the gunky layer of paint and shellac and get the board truely clean.
Going over the board with the denatured alcohol can be a messy process, so be prepared with plenty of steel wool pads and roles of paper towels.
This process should get you down to the original stained finish. The added benefit is that the steel wool can smooth out any rough patches leaving you with a very smooth board. The alcohol also helps, giving the board a warm glow and an almost satin-like finish. From here you can either re-apply a shellac to restore the original look or change the hue of the wood with a different color stain.
In our case, we plan on using a darker finish than the original. This will actually be pretty close to (but more attractive than) the color when we bought it, because the aged shellac had darkened the overall color over the years.