I use chemical paint stripper. First couple of coats I use a scraper. Then I move on to rubber gloves and course steel wool, where I scrub the frame essentially with working stripper. I then use more steel wool and scrub the frame down with soap and water.
I then inspect for flaws, or address any fabrication or weld issues I've been looking at along the way. Dress it up, then a final sanding job by hand, followed by a soap and water wipe down, followed by an acetone wipe down. Then tack cloth, then primer, depending on the duration it will remain in primer, and depending on what top coats I'll be using.
This method allows me to retain control of the restoration/modification with a hands-on approach. I get to see the layers of old paint, down to original in many cases for a color match. I get to see what primer (usually none) was used in the period, any welding errors, (I get off on seeing bits of MIG wire stuck beneath original paint) and a play by play rewind of history.
If this doesn't appeal to you, get it blasted. It's easier, less time consuming, less messy if you don't have the room. Heck, you can even pay someone to powder coat it afterwards, and avoid even being involved with the frame.
I wont speak for all powder coaters out there, but if I were applying PC and getting paid for my time, I'd have it blasted, period, because any missed paint will bubble in the oven. With PC, any substrate can cause an otherwise good application to look bad, and no one wants a reputation like that.
Since I paint my own frames, I have no concerns or questions about the stripping or preparation I've done before painting.