Not sure how old the shed is that you are renovating, but a big concern is whether it is old enough that the paint may be lead-based?
Your rules there may be different from here. The assumption here is that anything older than 1978 might have lead, and must be tested before renovation. You can usually get a lead paint test kit through hardware stores, at least over here.
You can also just assume the paint contains lead as you renovate (again, different rules?
?). Tarp the ground to catch as much falling paint chips and dust as possible. WEAR A PROPER DUST MASK AND EYE PROTECTION, recommendation goes for any paint, not just lead-containing. If soil around the shed looks like it has paint chips in it, I would scrape up the top couple inches to get rid of the lead risk. (
Final time ... Check your local rules on disposal of lead-containing soil and renovation waste).
General sanding recommendations: use a stiff wire brush to remove the coarse chips and flakes. I recommend getting a1/4 sheet pad sander equipped with dust collection. Check online reviews for models that are reliable, easy to use.
Good luck with it, you can do it!