I suggest you allow time to get through the traffic going to Old Trafford and the lack of parking!
Get off at Junction 19, get on the A556, turn left to High Legh on the A50 and then right onto West Lane. Then follow the Sat Nav to Partington then Carrington and you will go straight into Salford on the A6144. Mostly back lanes and you’ll miss everything. Don’t try it on a coach though as there’s a low bridge under the canal.