Try doing a mini mash/ brew in a bag for a brew. Get 3 lb of 2row, a pound of flaked oats, and whatever specialty grains you want for color/roastiness. Get them crushed. Put in a straining bag that is big enough (they should have these at brew store). Bring 1.5-2 gallons of water up to 165. Add grain bag and stir the grains around inside the bag to get them saturated. Make sure temp. settles in around 155. Put lid on and let it sit for 45 min. to an hour. After that time, have some 168 degree water on hand. Lift the bag out and rinse some water through the grain to wash out any remaining sugar. Don't squeeze the grain bag out, but let it drain out. Top up with more water and some extract and proceed just like normal. This might get you what you are looking for in a fuller beer. Also, a good way to dip your toe into all-grain brewing and you will see it is not much harder.