Best way to remove paint

You can do it you self but you will need enough Nitromoors, J-Cloth (not sand paper) and a lot of elbow grease that it's easier/cheaper to take it to a local powder coater as others have suggested.

If you insist on doing it your self the easiest way to refinish it that wont look like orange peel is to polish it with buffing pad and a drill and then clear coat it afterwards.

Angle grinder

Take stripped frame to an automotive bodyshop and have them dip it in the acid tank over night. Or have it sand blasted at same location where the heads of cars are rebuilt.

As far as removing paint, glass bead blasting is an option, and much kinder on the material.

Costs more...

Take it to a pro, not worth doing at home.

Agree with Tjuice. I left my very scruffy aluminium frame with a local (recommended) paint shop. They stripped it and powder coated it in a few days all for £50. Much better finish than most people would likely achieve at home. Unless they happen to be professional coaters/sprayers of course.

I can thoroughly recommend getting a professional to do all this for you.

I took an old frame and fork (both steel) to Armourtex in Hackney. For ~£50 (a few years back), they baked all the old paint off, aluminium oxide blasted it (gently), powder coated it and lacquered it. All over the course of about 4 days. A really lovely and very durable finish.

In the past, I have also stripped and resprayed my own frame. It was long, arduous work, and despite following all recommendations/suggested techniques, and taking my time over it, the finish was not even close to being as good as the Armourtex finish. And it was not overly durable either.

Are you looking to strip and repaint yourself or have someone else do it for you?
As suggested, Nitromors is your best bet for a home strip, it sometimes helps to score the coating to help the chemicals get under the old coating. If you can, strip it in a sealed container, heavy duty polythene bags are good. The reason for doing this is to reduce the time it takes for the Nitromors to oxides, as it oxides the stripping effects reduce and it can become snotty making it a bugger to remove. Steer clear of strong caustic / alkali strippers. One stripped, you'll need to jet wash the residue away, and now the real hardwork begins! You'll see lots of paint remaining in welds / tube joints that can be a right bugger to remove. Sand paper works well. To get the best final result, good preparation is key.
Sand blasting is still an option although I wouldn't recommend its use as a stripper, it's great at removing all the little paint bits stuck in welds etc. Where you need to be careful is with the type of media used. Stainless Steel is one to avoid, sand is an option as is aluminium oxide. Your basically looking at delicately prepping the surface for fresh paint rather than trying to remove swathes of old paint by ripping it to pieces.

Powder Coating is a good option, it's robust and will provide good corrosion protection, if you do go down the Powder route make sure the coater is used to coating bike frames and knows where to mask: BB, headstock, dérailleur hanger etc.

Muc-off

Nitromors is what I use on any metallic thing I want to strip paint from, got to wear protection though, face mask and gloves, then do it in a well ventilated area.

For painting, as long as you have the frame clean and get a good primer on it, spraying will be fine for a home job. Power coating is always nice though