Had the same problem with my 2009 Wildwood. No suction hose on the pump and no low point drains. I had to put 7 gallons of RV antifreeze in the tank for the pump to pick it up, and that was with the TT leaning 5 to 6 degrees towards the pump side. I think it all comes down to the assembler who installed the pump and line into the tank. How far from the bottom of the tank did he install it is a big variable.
By the time I was done, I had used 9 1/2 gallons!
Now, my new Lacrosse has the extra line on the pump that I just stick into the gallon of antifreeze. So, 2 1/2 to 3 gallons (probably overkill but, I want to make sure all lines are full) later and 15 minutes and I'm done!
I think installing the conversion kit is well worth the money, aggravation and time saving it saves you. That will leave you more time for