Cut in shortening and butter (or all the butter, if only using butter) until mixture is crumbly - a not so even mixture of little and larger lumps of flour covered fat. (betterbaking.com)
Fold flour mixture into pumpkin mixture until combined (small lumps of flour are ok). (sunnysideupsd.com)
Do not overmix (a few tiny lumps of flour may remain). (health.com)