This is the basic strategy that I used from AQ & BK level 35 to near max. As one or more heroes are upgrading (UG) and I am very low on DE, I start doing a few babyloon raids a day on easy bases to build DE. I also spend all extra loot on walls to keep from being raided, if possible. After hero(es) are done I raid as often as I casually can to get about 60% of the way to my next BK UG. When I have about 3 hrs to do boosted raids I make my final push to UG BK with babyloon or miner raids. I use these raids because they use very little DE and with the bonus in champs or titans, you can often profit 5k to 7k DE per raid, if you are lucky. When BK is UG, I keep going at the casual pace again without him to get to the 60% percent mark. I am pickier without BK and choose only easier bases that are loaded. Once again, when I have the time for boosted raiding, I make the push to finish getting the required DE for AQ UG. This usually takes a minimum of 3 days while BK is down. Since clan games, I try to time final push so that I can use the hero book reward to speed up UG. Remember, as a famous forum person told me (you know who you are, lol), “the secret to winning wars are high level heroes”! Good luck and have fun clashing!