Prepare
Take back what gets walked on
Pull up carpet, staples and nails, then sand the treads with an orbital sander, 80 then 120 grit, to strip varnish and wax: on a tread, paint only holds on clean, dull wood. Fill holes and splits with wood filler, sand again, vacuum, then wipe with a damp cloth.
Balusters and handrail are sanded by hand with 180 grit; an iron banister is wire-brushed and given our Multi-Surface Primer. On bare tread wood, apply our Multi-Surface Primer before the floor paint; on sound, previously painted stairs, sanding is enough.