"in the past i used a kitchen scale to weigh my pwe trades and added stamps as necessary. lately i've been getting more returns or complaints of insufficient postage. to prevent this i have since been using the USPS kiosks to weigh and buy postage for my trades. While this is a bit cumbersome (there are only 2 kiosks in my immediate area) i'm not handcuffed by the post office normal business hours or getting upcharged by clerks who think they need to know everything. (btw the kisosk will also sell international postage as well)."
I only go by kiosk now as it just gives me the price, avoids lines and, during these continued days of Covid, avoids people (I send my cards out at night). I spend gas to get there which is a pity, but if a letter doesn't arrive I know it's not on me.