Ever call somewhere to make sure they have an item in stock, then go there and find their "system" says they have four but they don't have any? Even the big boys like Boeing and Ford have put away their scanners and computerized inventory tracking systems to go back to flag systems where a guy raises a flag on the bin to call attention to low inventory.
Tracking product used (for ordering purposes) is better done by having an organized shelf and bin system and just having someone look at it to order more stock the way they do at grocery or big box hardware stores. Your designated "order clerk" should quickly figure out how much of what items are used in a particular time frame and will learn the lead times between order and get.
Keeping track of what, when and how much you bought can be done using the invoices and is what software is for. If you aren't ordering very large amounts this can be done with an Excel-type spreadsheet.