Most of my dollar store and garage sale purchases were smaller wins. For example, videos purchased for $1 would often resell for $8 to $10 on eBay.
Even with smartphones, having specialty areas will allow you to move quickly through garage sales and identify the more valuable items.
Finding great deals at garage sales is all about volume. You need to be able to move quickly from house to house
Most anything decent at a garage sale will be gone before 10 am, if not earlier. There will be others looking to resell items, so it will be essential to beat them to it.
Many eBay vendors offer free shipping, so it is important to keep shipping and packaging costs minimum.
Most people don’t seem to care if you are looking up items on your phone, though I’ve found it does make the negotiation process more challenging.