something simple I use to assist is a magnetic angle guide... get the one the right angle for your chain and just attach to the bar while you sharpen...
https://www.ebay.co.uk/itm/23569095...LZs0so9dwS7N9dgAAAAAA&loc_physical_ms=9189453
https://www.ebay.co.uk/itm/23569095...LZs0so9dwS7N9dgAAAAAA&loc_physical_ms=9189453
