The solvent-based stuff works pretty well on alkyd or oil-based paints, but loses IMO on latex or really-old paint. Citrus comes in spray cans, works in an hour or two, works great on latex, mediocre on oil-based. Sometimes it helps to alternate applications... and you'll probably need multiple applications anyway.

And it hardly ever comes off completely... then sanding is needed. Sigh.

The kind of respirator I'm thinking of is a hard plastic mask with a rubber skin-seal, and accommodates one or two filter cartridges (the solvent cartridge also handles dust). Basically an industrial low-end unit. I use one for painting, staining, stripping, etc., or when patgreene paints her toenails.

Ceiling suggestion: I've tried several approaches, and they all suck. Sandblasting has a strange appeal, after awhile. The least bad approach that I've found: Get wide strips of shelf paper, non-adhesive. Ladle paste-stripper on one side, and carefully apply the wet side to the ceiling. Secure it with pushpins, thumbtacks or small nails. Remove it the next day, or before the paste hardens. Sometimes the paint will stick to the shelf paper when you peel it off, otherwise scrape, reapply and eventually sand as usual (shakes head).

Messy and frustrating, no matter what... my sympathies.