Campaigns celebrate the volunteer sign-up like it is the win. It is not. The win is a person standing on a doorstep three Saturdays from now — and most portals lose them somewhere in between.
Treat the portal like the funnel it is. Measure the drop-off at every step: sign-up to first shift booked, booked to shown, shown to returned. Each gap has a design fix, and none of them are exotic — a shorter form, a same-day text confirmation, a shift that fits around a job.
"The volunteer who shows up twice is worth ten sign-ups. Design for the second shift, not the first click."
The campaigns that turn out their lists do the unglamorous work: reminder cadences that respect people's time, follow-up asks matched to what someone actually did, and a portal that remembers them when they come back.