Ever since I started winter sowing pepper seeds, I haven’t gone back to starting the seeds indoors. When I first started gardening, I assumed that starting these seeds under grow lights was the only option. My first couple trys at grow pepper seeds was an absolute disaster. In the end, I had little to show for it, aside from potting soil stains in my living room carpet. 
Fast forward a few seasons, and winter sowing peppers is my jam! Like most other plants, peppers can be started in winter sowing milk jugs or soda bottles. Here in my zone 6b/7 garden, I generally begin the process of winter sowing pepper seeds around mid March. By March, the days have started to warm a little bit, even though the nights are still cold.
As the seeds begin to germinate, I’ll need to keep a close eye on the pepper seedlings, as they are very sensitive to frost and cold temperatures. On nights when a frost is predicted, I will need to cover the winter sowing containers with some form or protection. For me, this means row covers. However, in the past, I’ve had great success with old sheets. Generally, I’ll keep bottles closed any time the temperature outside is below about 40F.
This is the first time I have tried to start peppers from seed. I planted the seeds on March 30 using the winter sowing method, plus the containers were in a cold frame so they had extra protection from the last few mild frosts of the season in our 8b zone (Pacific Northwest).
IT WAS AN EPIC FAILURE! Not even one pepper seed germinated. My seed was fresh, packed this year from Baker Creek Seeds. They were kind enough to send me replacement seeds but did not recommend trying to winter sowing them.
Your method of pre-soaking on the heat mat makes sense, so I will try that next year. Might even put the germination trays on the heat mat until the seedlings are well established.