Your technique is ok. The problem is the extension cord itself. Cheaper extension cables tend to bend, twist and tangle because either it has fewer but larger strands or the insulation being made out of poorly pliable material. Or a combination of both.
Do yourself a favor and make your own extension cable out of SJOW or SOOW wire cable. Not cheap but it should be the last extension cable you'll ever buy. Water proof, great resistance to most chemicals and uv light. The best part is it doesn't tangle, kink etc. The sjow are rated for 300v while the soow 600v. The sjow are suitable for most of a homeowner's needs. The soow just handle higher voltage and also has a very thick insulation. Both uses a rubberized insulation that has very high tolerance for heat or flame. If not on sale, expect to pay $10-15 for the male plug and $15-20 for the female end.
Those are some of my shorter 12 gauge extension cables. Also have some longer ones that are 10 gauge.
The thicker wires are the soow. All 12 gauge.