Urethaning my Woodwork

We've been renovating our old 100 year house for almost 20 years. I have learned a lot fixing up this old house. It was pretty nasty when we first purchased it. It had been a rental unit for proably 50 years or more when we first moved in.
I have stripped basically ALL the woodwork in our old house of all the paint and refinished it. Well, I think I may be doing my last door of the house, but I could discover something else down the line that needs to be done. I've left the kitchen and bathroom painted as I've discoverd those rooms don't strip as easily. Most of the other woodwork was easier to prepare as whoever painted over the finished woodwork the first time, did very little preparating (like sanding off the old finish), so the paint came off relatively easy it most areas.
I learned that the best tool for stripping the paint is a heat gun and stripping tool by hand. Most of the paint stripper chemicals I used didn't seem to work well, especially when I've left the wood trim attached, so adding stripper when things are vertical just doesn't work well. Be careful stripping the old paint, as some of it could be lead based paint and cause caustic fumes. You should keep the windows open and wear a mask. I did not and to my knowledge have had no ill effects, but don't blame me if you take this risk.
So what I've learned about Urethane (and I prefer urethane to varathane - not sure why) and I use the satin finish, but that's your preference. Always prepare the wood properly, you should sand well and put on your stain (more about that later). I applied the urethane with a foam brush in as few strokes as possible. The more you go over it the more likely you may get air bbbles. Also, apply it very sparingly, it should just be a thin coat, so you don't get any runs, drips or blobs. Let the first coat dry thoroughly (I wait at least 24 hours). Then take very fine 120-150 grade sandpaper and LIGHTLY sand again, this makes a much smoother finish. Wipe of the dust from sanding with a tack cloth (I just use a clean rag with a little paint thinner on it - which works fine) Continue to do this and your wood will be glass smooth. For any surfaces that we regulary touch or wash, I have applied 5 coats (trust me, it's worth the extra time), other surfaces, 3 is adequate. I recommend always using at least 3 coats. 2 coats will work, but it won't be as smooth or as durable. Always add a thin coat each time, once the finish has one coat, it applies very easily and it is really worth it. DO it!! You won't be sorry.
I'm on my 2nd coat on the door and I'll probably just do 3 coats and 4 or 5 around the handle and areas that get touched more. I'm also doing a small part of the hardwood floors in the hallways and I will definitely put on a minimum of 5 coats of urethane. It dries fast between coats (after the first coat) and the sanding is minimal, you don't want to sand too hard or you'll take off ALL the urethane, you just want to rough it up a bit, so sand lightly. So here are the steps in step form
1. Prepare your surface, remove paint, sand and clean
2. Apply thin coat of urethane with foam brush or applicator
3. Let 1st coat dry 24 hours
4. Using 120-150 grit sandpaper, LIGHTLY sand first coat.
5. Using a tack cloth or cloth with paint thinner, wipe off sanding dust.
6. Apply next coat of urethane. Let dry. Usually 1-2 hours.
7. Repeat steps 4 & 5 & 6 to achieve up to 5 coats.
8. Apply last coat.
9. DO NOT sand or wipe after last coat.